On the subject of machining....
With all the caulk that holds the window in place, I find it's difficult to get an idea of the actual window shape. I recommend removing one to use as a pattern rather than guessing with the window intact.
As far as I can tell, all four are identical in shape. Two are mirrored from each other. (Not sure if that is important; I don't know if Lexan has an indoor and an outdoor side to it.)
I personally used a jig saw to cut the portlights to size, fitted them, and used a sander to remove excess material where they would stick in the cabin top.
Good luck!
