I made a new mock-up with my fitting alterations : perfect !
Than, I finally found which fabric and trim I would like to use : the rest of my French Dress's mixed-silk.
"flat felled" sewing
Day 4 :
I finished center front with the busc & center back with 42 eyelets (fortunately I have my lovely Prym Pliers)
Now I just have to modify boning channel position :
in red, the pattern boning channel placement
in black / white, the new position whished