Good infos guys!

Multiflyer, my theory about side area is the following:if we look at the airplane from the side, let's draw a line on the thrust line. There will be some surface above the line (rudder fin tipically), and some surface under the line. If the two amount of area are equal (actually a weighted sum must be performed, in order to consider the distance of every piece of area from the CG) then we need no right thrust, since the spiraling slipstream does not produce the tipical yaw moment that requires right thrust. I'm sure about that last fact, since I've flown a depron biplane with a symmetrical fuselage around thrust line, and it didn't require any right thrust.

That will be a good result, since one of the most difficult trimming to do on a pattern plane is the yaw axis...