I wrote a long message a few mins ago telling about all the design parameters for bipes, but there was a posting error and I lost the message.

The long and short of it was:

Gap/Span is the important number, the bigger the better. You dont want to stagger the wings (can create unstable stall behavior, bad for a 3D model) and you want them to have the same angle of attack. You also want them to be the same length.

Otherwise, its a 3D aerobatic model, aerodynamics don't really matter much. Go with what looks right.