I installed a spring based aileron trim in my 6 and it is very effctive and noticable. I, like others, suspect other factors that are keeping it from working. All it does is apply a level of pressure against the control system, just like your hand on the stick does.
Can you estimate the amount of pressure that you must exert to hold the plane level without the trim system?
It's possible that you are too far out of trim from a rigging perspective and asking too much of the spring. You should be able to hold level flight with relatively limited stick force if you expect the bias trim to be effective. If this is not the case, you will either need to re-address the rigging or add a trim tap or wedge to an aileron.
I would also confirm that the servo is actually moving when you press the button. It could be a wiring issue or bad servo. If you add a lot of trim in one direction, you should see your stick pulled way over to one side while on the ground.
Larry