Jim,
I had to do a LOT of work on the windscreen recess on my car to get the glass to lay in right and then still had some issues that I had to live with. (I bought two windscreens, just in case.) Glass is funny stuff: while pulling the corner down when gluing in place will likely never be an issue, stresses could exist in the "ice" that would allow it to crack the whole corner off when you hit the first jarring bump or as the windshield heats up in the morning sun. (Glass is an ice of silica for all intents and purposes and, as an aside, I saw a program recently where they showed some amazing properties of metallic ices as opposed to the more familiar metallic crystalline structures, that is, amazing strength.) Many windscreens today are stressed members of the body and windshield fabrication techniques allow for this. But also keep in mind that some uninitiated passenger may reach up and grab the corner of the door opening to pull him/her-self out of the seat before you can stop them :-(
You may very well have already done this, but you might want to look closely at the recess to see if you can determine why the windshield is sticking up. While the problem could be the shape of the glass, the most prevalent fittment issue is in the lower corners: there would appear to be two families of windscreen glass - Australian and English. The former seems to have less curvature in the lower corners, not in the uppers as you have described. So, my guess is that there is some irregularity in the recess channel. ½" showing is really not a lot and some careful, very judicious sanding may allow the corner to rest comfortably in place or, at least, with less protrusion. I would look for high spots in the recess floor that you can feel as the likely culprit(s).
Often overlooked is the need for a ¼" gap around the periphery of the windscreen. Make little ¼" chocks to go along the bottom edge of the windscreen to check this and, who knows, just doing this may help with your fittment issue as well.
Regards,
Lynn