with reference to the windshield, mine is lexan, could easily have been made from thin plastic card, and it would have been quicker, and lighter, but I am a bit heavy handed so wanted something that would take some knocks. Its quite a complex shape, the curvature of the roof at the bottom of the screen, and the screen shape itself (remember mine is a 28, not 31)
So I made a cardboard template, fitted a false ply section on top of the superscructure for the screen to butt up against, bought some lexan and a heat gun, and made a form from an old biscuit tin and some old wood, heated the lexan up and teased it around the tin (and made a spare screen). It took a few goes, and it could be better. I bought some cheap plastic channeling from b & q for the screen frame, and using the heat gun formed that arouind the lexan, supergluing it on. I scrounged some off cuts of car window tint from a local supplier, and tinted the screen with this, and also did the cabin windows from inside, so all the gubbins inside the cabin isnt that visible.
The whole thing is held on with a home made plate either side, and 4 2mm bolts, so I can remove the screen in one piece for replacement if necessary, hope that helps