I have no scientific proof of the following, only experience with about 11 bipes I've built and flown. I have found that the relative incidence of the upper to lower wings have a big effect on how well a plane flies. If you want maximum ease of flying at all attitudes (aerobatics) all of mine have required the upper wing to have about 1.5 degrees less angle of attack than the lower wing has. I also find that all required right thrust and downthrust to fly nicely at all power settings. Realize that these have all been typical bipes like Aeromasters, Phaeton90's, Phaeton40's, Moth's and several sizes of Chuck Cunninghams Lazy Ace; all slightly overpowered. If I were designing my own bipe, I'd make sure I could easily modify relative incidences until I had the design well tested. Just a half degree change can make a big difference in how well it flys.