I've been using negative incidence in the right stab relative to the left stab for 20+ years. Geometrically straight and aerodynamically straight are not the same when there is a single propeller on the front of the plane (causing spiral airflow). When you have the amount of bias in the stab correct, the plane will have the same pitching behavior in both KE's, and then you can you wing incidence, CG, or thrust to perfect the KE. Mixers are not preferred as they will only be 100% correct at a single airspeed and angle of attack.

Regards,

Dave