I thought that polycarbonate cooled quickly (sometimes annoyingly quickly), but required a high temperature to form.
I'd guess that either that means that polycarbonate has a high thermoforming temperature (range) but a low specific heat, or that I just misunderstood something.
(That's one of the things I was thinking about when I wrote the post about how long and hard you need vacuum for... is brief high vacuum enough for thin Lexan like for RC car bodies, because after a few seconds it's cooled too much to matter anyway? Or should you keep heating the plastic WHILE it's forming... I can do that with my over-and-under, putting the platen right up under the oven.)