I test all your suggestions, and you were right !
The problem was the objective was looking for a precise trim setting, even if it is a reality a bad trim setting. So, instead of use the stick, then the trim to fix it, i must use the trim to find the trim setting require for the objective, and then, i adjust with the stick.
Absolutely stupid ! And never do that in reality… But it work for the mission.
Thanks for tour help 
