In 2001, Danièle Jay published an article on the website of ORA (Organisation pour la Reherche Astrologique) - 'Hémisphère Nord, Hémisphère Sud'
https://www.ora-astrologie.fr/articles-en-libre-accès

ORA is an association based in Lyon, bringing together astrology amateurs and professionals. It aims to develop and promote quality astrological practice.
They have a magazine 3*7*11 and some articles are in open access like this one.
Here is a resume of her article with an interesting perspective on Southern Hemisphere birth charts. (Google translation modified)
-------------
Ptolemy carefully distinguished the zodiac from the constellations of the tropical zodiac, as was very opportunely recalled by Pascal Charvet, happy translator of the Tetrabible (Le Livre unique de l'astrologie, Editions Nil, Paris, 2000), in a program by Marc Menant broadcast by Europe I on February 4, 2001. It was after having mentioned "the individual powers of the fixed stars according to the observations made by my predecessors", that the Prince of astrologers turned without transition to the study of the four seasons of the year :

“Spring is the most lavish in humidity because it diffuses when, the cold of the past winter, the heat begins. Summer is the most lavish in heat, due to the fact that at this time the Sun is close to our zenith. Autumn is the most profuse in terms of drought because the hot season has barely ended and has absorbed the humidity. And the winter is the most prodigal in cold, because the Sun is furthest from our zenith" (I, 10, p. 54). And Ptolemy continues: "This is why, even if the zodiac as a circle "does not have a natural and defined starting point, it is agreed that the sign which begins with the spring equinox, Aries, is also the starting point of all the other zodiacal signs" (p. 55).

We must understand the full importance of this statement. Aries is designated as the first sign of the zodiac, because it is he “which begins with the spring equinox” (the first degree of Aries, vernal point, is also the common origin of longitudes on the ecliptic and right ascensions on the equator). Therefore, the link is clearly established between the signs of the zodiac and the seasons of the year.
And it is immediately after having examined the various characteristics of the twelve zodiacal signs that Ptolemy deals with the particularly important chapter for the subject which concerns us today, that of the “affinities of the planets with the parts of the zodiac”. He declares :

“The system of domiciles is as follows: as, of the twelve zodiacal signs, Cancer and Leo are furthest to the North and closest to our zenith (place of maximum positive declination of the Sun), they are therefore producers of suffocating heat and atmosphere, tradition assigned them as domiciles to the largest and most eminent of the celestial bodies, that is to say the Luminaries. Leo, as a masculine sign, was assigned as domicile to the Sun, and Cancer, as a feminine sign, to the Moon..." (p. 64). And further: “To the star of Saturn, which is above all cooling, as implied by its nature opposed to heat, and whose orbit is the highest and furthest from the Luminaries, the signs have been attributed diametrically opposed to Cancer and Leo, that is to say Capricorn and Aquarius, with the additional reason that these signs are cold and wintry..." (p. 65).

Saturn is cold, it is logical that it governs two “cold and wintry” signs: it is said to be “dignified” in Capricorn and Aquarius. The Sun is hot, it is just as logical that it governs Leo, a sign that it is going through in the season “most prodigal in heat, due to the fact that at this moment it is close to our zenith”. The Sun is said to be “dignified” in Leo. It's summer.



It's summer in the Earth's Northern Hemisphere. And as everyone knows, it’s winter in the southern terrestrial hemisphere, beyond 23°26’ southern geographic latitude! In the Southern Hemisphere, can the Sun, a hot star, be “dignified” when it crosses the sign of Leo, even though it is, in this hemisphere, the coldest time of the year? You have to be consistent. If, as Ptolemy states, the dignities were developed in close correlation with the variations in the declination of the Sun and with the differences between the seasons of the year, and we have no reason to contradict him, we must draw all the conclusions for the Southern hemisphere: we must dare to say it, in the Southern hemisphere, the Sun will be “exiled” in Leo, as it is in Aquarius in the Northern hemisphere, and for the same reason. In the Southern Hemisphere, the Sun will be “dignified” in Aquarius in February, the “most heat-profuse” month of the year in this hemisphere. If we place ourselves in the perspective of Ptolemy and the astrological tradition, we see that it is strictly necessary to reverse the dignities in the southern terrestrial hemisphere.

But some will say that we should rather reverse the zodiac signs when we are in the southern terrestrial hemisphere. We don't know by what enchantment, the zodiac would suddenly turn upside down when we pass to the other side of the equator...

(…) Danièle Jay then goes on to show the calculations for a Northern and Southern hemisphere birth chart.

As Max Duval rightly says, taking the example of a southern chart cast not for the month of August, but for the beginning of February, "don't you find it ridiculous to consider the Sun 'in exile' in full hot season, (while) the length of the day is the same as in the Northern Hemisphere at the beginning of August? » (“L'Astrologue” n°118).

We must understand this well, the planetary dignities with which we are accustomed (Leo domicile of the Sun, Cancer domicile of the Moon, Gemini and Virgo domiciles of Mercury, etc.), and which are based, as we have seen, on the variations of the declination of the Sun, therefore on seasonal variations, as Ptolemy explained so well, were in fact constructed in and for the Northern hemisphere, at a latitude of approximately 30°N, and with a temperate climate. The Ancients had little concern for the Southern Hemisphere. However, for the system to maintain its internal coherence, it becomes imperative to reverse planetary controls in the Southern hemisphere. The tropical zodiac is first and foremost an astronomical data, linked to the apparent path of the Sun (ecliptic) around our planet Earth in geocentric perspective, - course which, combined with the inclination of the terrestrial axis on this ecliptic, gives rise to the seasons, real foundation of planetary dignities.

Thus, in the Southern hemisphere, the Sun will be exiled in Leo, dignified in Aquarius, exalted in Libra (time of the year when, in this hemisphere, the length of the day begins to exceed that of the night), falling in Aries (time of year when, in this hemisphere, the duration of the night begins to exceed that of the day). The inversion of the dignities of the Sun obviously leads to the inversion of the dignities assigned to the other stars. In the Southern Hemisphere, the Moon will be dignified in Capricorn, exiled in Cancer, exalted in Scorpio, falling in Taurus. Mercury will be dignified in Sagittarius, dignified and exalted in Pisces, exiled in Gemini, exiled and falling in Virgo; And so on. It will also be necessary to invert the Triplicities, the Terms, the decans, the value of the Lunar Nodes (the South Node will take a North Node “value” in the Southern terrestrial hemisphere, and vice versa), the signs of short and long ascension. It will also be necessary, as Joe Fallisi suggests in his article “Maradona e l’emisfero Sud”, to reverse the zodiacal latitudes. On the other hand, there is no reason to invert the value of the Black Moon, the major axis of the lunar ellipse having no relationship with the side of the ecliptic.

In the same issue 118 of “L’Astrologue”, Max Duval deals with the particular case of intertropical zones, between 23°26’N and 23°26’S. In these zones, all places that are in the northern hemisphere of the ecliptic at the time of birth will see planetary rulerships identical to those in the Northern hemisphere. On the other hand, all places which are in the southern hemisphere of the ecliptic at the time of birth are subject to the necessity of the inversion of rulerships, whether these places belong to the northern terrestrial hemisphere or to the hemisphere terrestrial South. Thus, it is the ecliptic and not the equator which is the “border”, as far as planetary controls are concerned. Readers interested in the subject can refer for more details to the article by Max Duval and to my latest book 'Ciels et destins', published in Paris in February 2000 by Editions Dervy.
---------------
(Here is the chart of Nelson Mandela as per her specifications)

Let us consider as an example the sky of the immense Nelson Mandela, born in the middle of winter, on July 18, 1918 in Umtata, South Africa, at the corrected time of 2:48 p.m. (12:48 p.m. UT), at 31°35 ' South geographic latitude and 28°47' East geographic longitude.

The MC at 4°26' Virgo, a sign which takes on a Pisces "value" in the Southern hemisphere, is governed by Jupiter, angular in house VII, in sextile configuration with the upper meridian and in conjunction with Pluto. This is a good omen, except that Jupiter is falling, and injured by the square of the Black Moon in X. Jupiter expresses well all the apparently insurmountable torments that he had to endure to access a position of power.We know that Mandela spent twenty-seven very difficult years of his life in South African jails.
But in fact, by which planet is the XII house of seclusions governed in this nativity? Given the career of Nelson Mandela, this planet should stand out firmly in the map. The ruler of XII, whose cusp falls in Scorpio (domification Placidus), is none other than Venus. However, at first glance, we see the planet positioned on the western horizon, in partial conjunction with it, which shines with all its power of action and directly injures the AS of the most famous inmate in the world. It is also conjunct with the South Node, which in the Southern hemisphere takes on the value of the North Node - one of the paths of life clearly had to pass through the tyrannies of the ruler of the XII, a house all the stronger because it shelters an exalted Moon in Scorpio! And it is Venus who is called upon by Direction during the first arrest of the activist (AS quincunx Vénus in Primary Direction), and during his sentence to life in prison and during his transfer to the Robben Island penitentiary, which inaugurates a very harsh eighteen-year detention (MC trine Venus). Let us not be surprised that the Direction presiding over this imprisonment is formed by trine: Ptolemy made it clear, the trine takes on the value of a square in signs of short ascension.

And the AS? At 22°17’ Sagittarius, a sign which takes on a Gemini “value” in the Southern hemisphere, AS is governed by Mercury. The latter, placed in one of the Terms of Venus, clearly expresses the civility of the physical and moral person. Located in IX, closely conjunct the lord of IX dignified in his house (Saturn in Leo - Aquarius value), to the sextile of Mars also dignified in Libra - Aries value, the lord of the ASC directs the personality towards tireless and ultimately victorious pursuit high objectives, those of the 9th house: Mandela has the weapons to carry out his ideological and revolutionary fight for the liberation of the black man (Leo taking the “value” of Aquarius in the Southern hemisphere).
But Mercury also receives the quadrature of the exalted Moon in XII, therefore very powerful: this means the pitfalls, the trials, the confinements, which will long thwart and delay the realization of its immense ideal of emancipation. Mercury is intelligence. Saturn, conjunct the ruler of the ASC, is determination, endurance, interiorization. It’s also loneliness! Without even mentioning prison isolation, we can allow ourselves to recall what Mandela wrote about himself, comparing himself to a childhood companion: “...He was extroverted, I was introverted (Saturn). He was cheerful, I was serious (Saturn). He succeeded effortlessly, I had to work hard (Saturn).” And further, “I am someone who seeks company, but I like solitude even more. I welcomed this possibility of being alone, to think and organize” (Un long chemin vers la liberté, Editions Fayard, Paris, 1995). Don't you have to have a dignified Saturn and ruler of IX to savor the fullness of isolation!
Let's hope that this little analysis of Nelson Mandela's theme will have convinced us of the need to reverse planetary control in the southern terrestrial hemisphere!
-------------------
Comments: It would be interesting to hear about our friends in the Southern Hemisphere and what is their approach by experience.

In the foreword of 'Pour une astrologie de l'événement' from Danièle Jay, François Saison says:
"Danièle Jay, who has been passionate about astrology for nearly 40 years, met Giuseppe Bezza in 2000, then translated his most important articles into French. Its mission is to transmit this lost knowledge by making it accessible to everyone."

As this is the Traditional forum, it seems appropriate to note that (tropical) astrologers have been debating this question at least since early modern times, presumably as a result of European exploration (and exploitation/colonization) of South America and Africa. Morin de Villefranche has been mentioned in a couple of other threads recently, and I recall his touching on the isssue somewhere in his Astrologia Gallica, though I haven't got the reference handy. And I know that Luís Ribeiro is knowledgeable on this issue; he may or may not have discussed it in his published (academic) writings.

this also brings up the issue of what are the differences between the signs opposite one another? this is also a topic morin did comment on - as memory serves - the opposite signs share much in common... i also don't have immediate references available to share, but i know this from reading morin..

Ouranos wrote when beginning this topic:

We must understand the full importance of [Ptolemy's] statement. Aries is designated as the first sign of the zodiac, because it is the [sign] "which begins with the spring equinox"(the first degree of Aries, vernal point, is also the common origin of longitudes on the ecliptic and right ascensions on the equator). Therefore, the link is clearly established between the signs of the zodiac and the seasons of the year.

Of course the northern/southern hemisphere problem applies only in the tropical zodiac as seasonal characteristics aren't applied to sidereal signs anchored to the stars or an equinox date. Astrologers in modern times have noted that observed traits of the zodiacal signs don't differ between the northern and southern hemispheres. If the sun is in Leo, the sun behaves in the same way in either hemisphere.

An important question is that Ptolemy was simply mistaken when he attempted to link seasons to sign characteristics of the zodiac: a very possible error which has resulted in a myriad of questions for astrologers, and which did a great deal to establish the astrological tropical zodiac.

The change of seasons mainly involves fluctuations in temperature, which affect human activities and moods. The sun simply moves between the Tropic of Cancer and the Tropic of Capricorn.

The temperature in Taipei and Sydney (Taipei in the Northern Hemisphere and Sydney in the Southern Hemisphere) hasn't experienced as significant variations as the temperature difference between Taipei and Kyiv (both in the Northern Hemisphere)!

I have made a big mistake!

The difference between the Northern and Southern Hemispheres is the length of daylight hours.

In fact, the length of daylight varies even between different longitudes and latitudes.

Previously, I had only read about this in books, until I experienced it firsthand.

Today is June 12th.

I used to live in Huwei Township, Taiwan, located at the following coordinates: 120E26 , 23N43

Today in Huwei Township, sunrise was at 5:10 AM, and sunset will be at 6:46 PM.

Now I am in Changsha, Hunan Province, China, located at the following coordinates: 112E58, 28N12

Today in Changsha, sunrise was at 5:30 AM, and sunset will be at 7:25 PM.

How did I discover this? I suddenly realized that it was past 7 PM, and it still wasn't dark.

Previously, I watched a video of French President Macron announcing the dissolution of parliament. The news report said it was 9 PM, but the video showed daylight outside. I thought the news report was mistaken. When I checked, I found out that sunset in Paris was at 9:54 PM! (I was shocked.)

So, I think I need to get out more. Staying indoors and reading books isn't enough; knowledge from books is hard to understand without personal experience. I need practical knowledge and experience. (I still highly value book knowledge - these are precious experiences.)