When you enable the trimmer, Just like in real life you lose the stiff resistance of the stick (for a traditional spring joystick it would feel as if the springs in your joystick disappeared), however when you release the trimmer instead of the stick staying in the position you had it and regaining resistance, the the joystick re-centers as if you hit the trimmer reset. The stick should stay where it is when you take it out of trim, not snap back to center position. So essentially no functioning trim with a springless force feedback stick .
The only workaround I found is to get your aircraft at the pitch/roll and speed you want it, enable the AI auto-flight then take back controls. This essentially does what the trim is supposed to do but again the joysticks stays in the center but at least it keeps the pitch and roll where you want it.
This is properly modeled in every other helicopter module, please keep in mind there are no springs in a force feedback stick it is controlled with an electromagnetic motor, and is a much more accurate representation when properly modeled.... I.E. If i trim nose down on an aircraft you can watch my joystick slowly creep forward by itself, creepy and cool.