There is a P90 build thread with lots of good info. Like top wing incedence changes, stab incedence changes, landing gear and so on. The top wing incedence moving to -1.5 deg did the most good in flight performance on mine. I would have liked to have changed the stab incedence to about +1.5 deg cause I flew with about 1/4" down elevator trim all the time. And make sure you put 4 ailerons on it, makes it a whole different animal.

So far, its one of my favorite biplanes.
Edwin