I was building a 125% sized plane from original plans. The plane designer suggested 6mm depron both upper and lower surfaces to effect the scaled up size. However, the 6mm foam upper surface didn't bend as easily causing the further aft high point. Airraptor hit the nail on the head. The wing flew just fine. See post #60 and then a few posts later for flight report in this thread, http://www.rcgroups.com/forums/showthread.php?t=2160082