GRinRI, I run the stove from 250* to 400* most of the time. I did hit a peak of 525 durring the -20* weeks we had. That was actually shortly before the glass cracked.
Oliver Power, Thanks for checking. That is what I needed to know. Looks like mine is realy warped then.
rburg- Not an illusion I am afraid. I measured the 3/16" dip inward off a straight edge.
I'm glad I have not installed my new glass yet. Otherwise I might have cracked it putting it into a warped frame. I will ask Hitzer if it is a common problem, see what they say. If it is just a fluke, I will price a new door. If it is common, I'll burn it as is as long as it still seals OK.
Thanks to all for the help.