Thanks Lee, I learned that same trick also. But as luck would have it, the one with the problem had that bump in the middle. The really interesting thing about this was that if you (or maybe 100 different people) took that bonnet out and felt of it, looked at it even carefully without using feeler gauges and a known flat piece to check it...you would probably have been willing to swear under oath that it was nice and straight and flat. But it wasn't. Overtightening is what caused the deformity. This piece needs to be snug but not tight to the point of warping.
