On my Extra 300 (VF), I used a strip of white sign vinyl on the underside. I reflexed the aileron all the way up and placed the sticky-backed material right into the space. I used a piece about 1" wide and the full length of the aileron - bottom side only. It doesn't show at all and doesn't inhibit movement to any noticeable extent. Remember that you do not need a lot of aileron throw for this bird. (The Extra and the Edge are quite similar in terms of performance.) The clear packing tape will work as well but is not as tidy.

Ross