Joe, I will see if I can get a good pic of the inside clearance of the smooth engine cowl with the bump installed. It is the fuel rail for the fuel injection that gets very close to the top cowl. When I built mine, I seemed to have everything lined up but gravity pulls my cowl down about 1/4 inch at the prop spinner such that I can see the back side of the spinner a little bit. Back at the fitting of the cowl bump I seem to recall I had about 1/4 inch of space between the cowl and that rail fitting. I am not certain that the cowl would not rest on that rail if my bumps weren't installed given the fact that gravity pulls my cowl down a bit.