You guys are impressive! No way I would ever struggle through all that. Did you consider spray-on contact adhesive, in a rattle can?
I have cut windows in Kasiner, CRC, Speer, Mac Shops, and K-Line extrusions. Far easier than using plastic overlays. With a small belt sander you can remove corrugations, although I used an end mill on the K-Line.
I may never cut another blank. Between K-Line and Sunset, I suspect almost any variant can be had. Far cry from the 1970s.