I'd give it a bit of time- Mine did the same thing and I was thinking that I left it too long- but a week later and the corners are laying much better with not nearly as much of the warping that was present when we first put the window in...

http://i1078.photobucket.com/albums/w497/slawnski/1964%20chevy%20c-10%20Montana/ddd8c879.jpg

http://i1078.photobucket.com/albums/w497/slawnski/1964%20chevy%20c-10%20Montana/75ca5586.jpg


1954 Chevy 3/4-Ton Chevy
"Mo"
1948-53-54 "Mixed Bag" Chevy Stakebed
"Basket Case"
1952 Chevy 3/4-Ton
"as yet un-named"
In the Stovebolt Gallery
Lots of pictures