Heh, I hold in my hand a dime. Upon examining it, I'm glad I stopped when I did. I actually took off a large amount of material with 400 grit getting the thing flat. It was disgustingly warped. The outside edges and center were about .5-1mm higher than the doughnut shaped depression. There's no way that the doughnut area was even in contact with my bowed HS. They're both flat now and the temps dropped significantly. Winter idle after the lapping was around 25-30C and summer seems to be 40-45C. Looks like it's averaging about 15C over ambient. All is well now.