On my pattern planes, Osmoses, Axiomes, Accuracy and Amethyst, none of them require any rudder input in or out of an attitude change, so I agree with Scott, it is a different problem.

Jim, have you though about increasing the vertical stab area for test? I mean form the L.E. fabricate a balsa piece you can tape on the LE of the vertical stab and then fly test?
I could give you more answers between the props and the V Stab area.

Regards