63 Windshield fitting problem

[welsh kev]

The guy who's renovating my 63 GMC has hit a problem with re-fitting the windshield.

Glass broke when he took it out so he's fitting a new one. i had supplied him with a new (as I thought) weatherstrip which I had bought in Canada in 2007.

Problem is that the glass keeps popping out in one corner. He has consulted a professional fitter, whose opinion is that the replacement rubber was probably old stock and had lost some of its elasticity. He tried heating it up in water to soften it but no luck.

Anyone come across this problem before and can suggest a fix? Need the truck on the road ASAP since I'm getting married in a few weeks and both future wife and I want the truck to be part of the wedding!