I've done windshields before. And just took the rubber gasket, set it out in the sun ( or heated it up). Put it around the windshield. Then took a long enough piece of string, and stuffed it in the groove where rubber seals on the windshield opening. Set the bottom in place. Then pulled on the string while someone was pushing on the window. When you pull on the string, It forces the rubber to set in place. If you do this, just make sure that you lube up the string first. It makes things a whole lot easier. At least on VW's it does...
