I had a hard lesson figuring trim myself out.
The thing is, that if someone has a force feedback joystick, its working different than with normal joysticks, where you use the "trim and center" method.
I didnt know this at first, and I always wanted to center the stick but it just made abrupt movements.
Finally i found out that with force feedback joysticks the developers intented to make trim much more realistic and if you trim you SHOULDNT NEED to move the joystick to the center, but the forces will reset and SHOULD hold the joytick in the position where you clicked trim. This thing WOULD have been great but actually there is some stupid bug with the force feedback interface of the game, and the trim forces on the axis are too weak to hold the stick there. So it kicks back and makes trim with force feedback useless.
And thanks to this bug, i cant use my force feedback function of my Saitek Cyborg EVO Force, because trimming is impossible. So i just disabled FF from the config and use it as a regular joystick.