I have assigned buttons on my joystick for raising and lowering the flaps and they work fine. When I press the increment flaps down button, they will lower incrementally. The reverse is also true with the raise flaps incrementally button. I don't know why (and can't think of any reason why) it won't work correctly.

As for the Thrust Reverser, I only use the F2 key because it's not possible to set reverse thrust on my joystick. But, like the flaps buttons, I can't see why you can't get it working correctly.

Mark