Some of the engineers can give you a much better answer but I have a couple of very old 1/2A trainer kits out in the shop with flat bottom wings and no dihedral that are only three channel. The little three channel planes I have built over the years all had the dihedral but these were newer kits.
If I had a good little RC 1/2A engine I would build one of these old kits and find out. I like three channel planes and think they make great trainers so a student lears throttle, rudder and elevator control.