Try the mixing, you may find that on a biplane you like it on all the time. I have a Byrons Pitts that has quite a bit of roll and pitch coupling that I mixed out. What I found is that all maneuvers became easier, including landing and take off. When I give it a little rudder on landing or take off the coupling is gone making it easier. Most computer transmitters today have multi point mixers making it less likely that it will do something you don't want at different rudder deflections. As 3drc has stated mixing may make some 3D a little harder, if not impossible. Today most people do not use a biplane to 3D anyway because of the coupling issues.

I eventually took the mixing off the switch after discovering that a couple of times my sloppy flying (ok...more than usual) was caused from the switch being off.