Vacuum formed parts need to be removed from the backing sheet. While I did not do it in this example, it would be easiest to see progress if we primer the plastic sheets in a contrasting color.
Above and below, I am using a purpose designed plastic cutter which I drag with one edge perpendicular to the sheet. Below, you see a curl of the plastic being removed.
After a few passes, you can flex the excess sheet back and forth to snap it off. Don't toss it yet. Actually, I never do!
For inside cuts, like windows, I scribe around until I can push the piece out...
The inside of the sheet is inspected for translucent areas. These get reinforced with the strips I saved. Use cyano-acrylate glue so as not to melt through the plastic sheet. Another product I have been using more often is epoxy putty. This is not only to reinforce translucent areas, but to fill the reverse side of the many pips used during the manufacturing of the vacuum-formed sheets. In this manner, I need not worry about cutting through the sheet when removing the pips from the face of the sheet.
To hold the edges of two parts together, I have used binder clips and run a thin cement to glue them.
I hope this helps,
