I'm sure others have had this issue too, Jim. Maybe someone else has a good idea. I bonded (Hysol 9460) and riveted ("soft" aluminum AN rivets) thin strips of aluminum to the lower cowl along the inside of the flanges just to give them a little more stiffness when engaging and disengaging the Camlocs. If you were able to bend a small flange on an aluminum strip, or even just use a flat strip, you could bond something like that to the upper cowl also, on the inside surfaces of both sides just above the actual mating surfaces, and that might help keep them flat and from "scalloping". Ideally, those mating surfaces could probably be a little thicker. That is kind of a common problem with fiberglass cowls in general. I really like the cowls being made by (for?) Van's & others that are fabricated as a double wall honeycomb structure. Still very light but much more stable and stiffer.