Your skill and craftsmanship never cease to amaze me, Charles! I've been watching this project evolve with GREAT interest and have to say that that cab is a thing of beauty! This is one of my favorite trucks, from this era. When I was on our local Fire Dept., back in the '90's, our township pumper was a '66 L-1800 built by Howe Fire apparatus, in Anderson, IN... (I live just up the road, in Summitville...) I've wanted to model that truck, for years! The truck still exists, now owned by one of our local firefighters, so I'll have access to it for pictures , measurements, etc... I do wish you the best, on this! I'd love to acquire one (or more) of these cabs, when you're ready to cast them! As for the windshield buck; If Renshape doesn't work for you (I think it will), have you considered shaping the form from a chunk of Bondo? I know a 1/72 aircraft modeler who uses this technique to make bucks for aircraft canopies... I think he uses an automotive wax on his bucks to help with adherence issues.