RE: Sig ultimate biplane
Increase the aileron size, that is the planes weak point. Flew mine with a .51 and was alright. I put a .90 in it and it was great. Move the CG back and the harriers/hovering becomes easier. Blenders and flat spins are cool. Look in at my models or gallery and you'll see the big one I made by doubling the plans. That plane is a 3D monster.