Expo, I start at about 40% and work from there, I like a soft center. I have only mixed in the aileron and rudder on one plane, a Giant Bipe. I had it on a switch and only used it at shows to help smooth out my turns without doing any of that thinking stuff, I had 10 or 12%mixed in, that's not a lot but it worked fine. Before that I had learned years before to use my rudder so it wasn't really a must do thing. Nix the idea of the flaperons, not needed on a Cub.