One thing to watch out for when modifying wings for bolts... espically the tower trainers. I recentally had a student that did the same thing, modified his tower trainer .60 for wing bolts. First flight it was flying around fine until the section of the wing where the bolts went through ripped away from the rest of the wing. He was lucky, since tower replaced the plane for free, even though he modified it. However, he now uses the bands on it and other planes that he modified in the same manner.