I cut down the original perspex (plexiglass) window from the old cabin. My 250mm table saw was very good at cutting the perspex - clean straight lines but I could also rotate the sheet against the blade to round off the corners smoothly.
Luckily the perspex bends more than 6mm ply, so it maintains the curve of the front panel. It was quite a fiddly job sealing with silicone because of the curve, but with help from Dilys in the cabin and me outside we tightened the bolts one by one, like the riveters did in days gone by.

You can just make out a triangular ply filler for the remains of the forward side window; the filler is cut from the front window waste.

That wide expanse of front panel is broken up now and the cabin is lighter and brighter inside.
As Al said, it's good to see where you are going.

-Paul