BTW, following the petorisis' post, I had an idea of refreshing my memories of Schmidt's Teachings on transits. And indeed, I found something not yet very explicit, but pertaining to the topic.

1. First, in the foreword Shmidt cites...Abu Mashar's work on solar revolutions:

"For, in the revolution of the year, the star often comes down to its own fixed degree, and often to the zoidion yet not the degree. At the times in the revolution of the year when it should come down to the degree in which it was at the fixing or to the bound in which it was, its signification will be perfect. And if the star in the revolution of the time is in a certain zoidion, then retrogrades back to its place at the fixing, it also has some signification in this way But when it should come down to the place of another star, one must investigate in a threefold manner".

Well, Abu Mashar clearly means the case when a planet has not one but three returns, of which the first one already took place before the solar revolution, but the planet will still come back to this place during the year to come. Unfortunately, he doesn't specify what exactly it means

(speaking of Saturn and Jupiter : their motion being as slow as it is, we can safely consider that any transit to radix is already imprinted in the solar revolution even if yet only by sign)

2. Dorotheus, p3. : gives an example of a bad Mars or Saturn transit, then "And stations in such ingresses by transit are also worse"

That's only one phrase, but an important one! Not clear though whether the stations are supposed to aggravate the already bad case because of the retrograde motion (bad condition for a planet) or whether stations are intensifying the transit or whether it's because stations make it all last longer.