hi,
been reading this thread, I have an ESM P-47 with the bubble canopy, they are a fairly hard material of some kind, it is .5mm thick, I have rung a few plastic suppliers, for Vacuum forming, the word is PETG the stuff they use for soft drink bottles, comes in a 2400 x 1200 sheet, Aus, $25 plus GST. (Grand Scale Theft)

the P-47 canopy took a bit over 1kg of plaster of paris, I gave the inside of the canopy a light spray of "INOX" then wiped it out, the plug came out without any problems.

HINT, if you get the chance, make a frame to hold the canopy in, I didnt and have a flat spot, can be fixed.

BTW if you use a good Tupperware container to mix the Plaster of Paris belonging to "you know who" MAKE SURE TO WASH IT OUT BEFORE IT SETS.

I am still building my model, the canopy has not been fitted, decided to make a plug. Just in case I break one.

happy flying. Oldtimer.