RE: Biplane trimming problem
Relative incidence has a big effect. On over seven large bipes I have had, they all flew best with the upper wing at minus 1.5 degrees relative to the lower wing. Also, they all had the lower wing and the stab at the same incidence setting with 1.5 degrees right thrust and 3 to 5 degrees downthrust. Now as to downwind versus upwind, it makes absolutely no difference. The plane is in a moving mass of air and doesn't know the difference between downwind and upwind. Now, you on the ground, may notice a difference in speed relative to you but, the plane doesn't know this and will fly the same whether going upwind or downwind or crosswind as long as you are higher than the turbulence caused by ground contours or buildings.