Looking here:

at a 380mm length, 125mm drop post, is G @ 195mm the measurement from top of seat post clamp to the bottom of the seat rails?

As i’m unsure what hauteur du chariot means.

With my current rigid post, i can ride it at a maximum height of 195mm from top of seat clamp to bottom of saddle rails, but no more, so a 125mm could just fit.

Failing that i guess i’m looking at a 100mm post.

Using a Fizik Gobi, so i guess i’d need to stick to that (no longer make my model) or a lower height saddle. Which, speaking aloud, may make a 100mm post a safer buy.

Ta

I would say that the top-most line represents the seat rails, which would be about 35mm above the top of the free stroke of the post.