Hard top door window seals

[Brave Salmon]

I am getting started on fitting the windows to my gard top. The flange for the felted seals was nearly 1.5" so I trimmed it back to 3/4" and now I have to thin the portion where the seal is pinched on down to 3/16 so the darn seals will fit. It's a laborious process but then, what isn't on these things. Does anyone have any input on the best way to do this project? I am going to use the internal frame posted here recently but I am really worried about that first cut in the top of my doors. It scares the hell out of me to do this blindly with only the book as a reference. Please help..:confused:

Thanks,
Tom