Only thing I have seen to get it really tight, is to install " cam -type " locks ( similat to levers on casement windows in a house ) on the inside window pillars to pull the frame in tight. Saw a '46 with stainless levers - looked pretty good and Owner said it worked wonders.
Actually, I believe the cam-type locks on the 46 trucks were factory. My '46 GMC has them. As mine is being rodded and I don't currently have a windshield frame, I'm V-butting the windshield to avoid this issue.
