ORIGINAL: Bax

Usually, with model biplanes, the upper wing has an angle of incidence set about 1 degree or so less than the lower wing with respect to the fuselage datum line. This helps the model "track" better at higher airspeeds, such as in downlines and the backside of loops. As far as one wing stalling before the other, theory would tell you that you want the more-forward wing to stall first so that there will be more of a nose-down pitching force at the stall. In practice, it really doesn't much matter with models, and with real biplanes, the optimum angles for the wings were found in flight test. What works for full-size aircraft doesn't always translate to models because while models get smaller, the air doesn't and has different effects with smaller objects.