the plans show it at the mid span on each wing. I am not asking what the name of this piece is just is it better to have on the top or the bottom. The plans show it on top of the wing. remember this plan has no air foil. I would like to have it on the bottom of the wing if it isnt needed for aerodynamics on the top.

My dad and I flew this in the late 80's and flew fine as long as the engine was running at half power or better. less than that and they turned into a guided rock.