I have been flying Bill Evans designs for many years now. I have modified the airfoil platform thru trial and error and came up with something that looks very aggressive and actually improves the flight performance. I put a slight total wing positive dihedral (about 12 degrees) and on each wingtip I put a slight down dihedral (about the same 12 degrees). The outer wing portion that has negative dihedral is at the point of 15% to 17% of the total wing half length. See the attached pictures of my flying squadron.[img][/image