Hi. I found this old thread and wanted to relay my experience.
I got my parts from AH Spares in GB. Fine quality.
Gasket went into the frame, no problem.
I wondered if it would best to do the bottom first, just because I couldn't imagine getting the glass corners into those deep recesses in the rubber.
Don't do it this way.
I made a couple tools from "hard" wood. Actually it was stir-sticks from a paint store. Not quite sharp on the end, but thin.
I liberally lubricated everything with rubber lube retrieved from the tire machine at the local garage.
Then I did like everyone else says and inserted the top first and maybe a bit less than half the sides. I realized that one of the tools would be better off being a bit more blunt, so I filed it down. This is the tool I used for just about all of the installation.
Then I did just about what ibcfan said and pushed the rubber past the glass from the outside. I worked my way down to the bottom of the windscreen and when I approached the bottom I simply pushed the entire rubber corner past the glass, again from the outside. I never needed to try to pry the rubber past from the inside.
From there the bottom went in easily because the frame flexes a bit, then just pulled it together.
I had previously made a tool for the locking strip on my hardtop window, but it was too big for the windscreen. I simply lubed the strip and gasket, and pushed it mostly in by hand. The wood tool finished the fitment to get the strip all the way under the gasket.
It didn't take more than a half hour.
I had read all about the horror stories on the net, but it really wasn't difficult at all. It's the lubrication. (In danish "det der smøres godt, køres godt") or: That which is lubricated well, goes well.