I added an extra 2 degrees of right thrust when I went to 3 blades. Plane tracks well.

Be sure to do your pull up right to left, and left to right. This is to make sure its not "weather vaning" into the wind (with respect to the ground).

Don

P.S. Also do this. With the plane inverted (aileron trimmed) cut the throttle and add some down elevator to keep it level (as if entering a spin). If the plane starts heading off (rolling off) to the right then add a couple of clicks of left rudder. Do this test again, and if it still does it, then add negative incidence to the right wing, if you can. This could be contributing to your trim issue.