First off, let me suggest a less dramatic chop. 4" is a little drastic and will give it a pancaked look. There are other alternative to keep from having to cut the glass at all. The best part is, if you get a rock chip, you get an original windshield and go on. Here is a picture of a '50 Caddy I did a couple years ago. It has been chopped 2.25" which is most we could go without cutting the windshield. The roof was moved forward to mate up with the A-pillars and the original rear glass was replaced with a donor from a '47 Packard sedan. The rear glass was leaned forward and sail panels were shaped to fill in the area which was once wrap around glass. As the old sayin' goes, a picture is worth a thousand words!
This shows the upper windshield channel removed. This is to gain the room needed to slide the windshield up into the roof cavity. Some thinking had to be done to make it work out, but mission accomplished! The glass is now glued in with urethane, just as new vehicles are and the original stainless trim was used to give it the right look.
In this view, notice that a section of the roof was cut out ans slid back 2" to make the quarter windows line up properly. They now work just as they did originally, but just don't roll up as far. Being a hardtop, it was crucial to make these line up properly for a good seal with minimal work. Also the Packard backlight frame is sitting in place and the masking paper is used to make a pattern for the sail panel. As it turned out, to look right, the Packard back glass had to be flipped upside down from it's original placement in the Packard. I guess you could say it 180 degrees out!!! ' with that mechanical lingo!!
Here is the finished product. Well, almost. The sideglass and trim isn't installed in this pic, but you get the idea of the area around the windshield.
Metalshaping & Kustom Paint