Back in the 1960s, this Mattell toy was hot—literally. The Vac-U-Form let kids mold shapes out of heat-softened plastic by sucking it over a form, just like RC bodies are made. Various forms were offered, including trucks and planes. The Mattell Vac-U-Form is still a sought-after item on eBay—scale modelers use them to make and duplicate clear canopies and all kinds of stuff.
A heated plate softens the sheet plastic, then you flip it over the form you want to mold. Pumping a lever sucks the softened plastic over the form.
This pic is from a current eBay auction. You still have time! Or, just get a new vacuum former from Micro Mark:
If you really want to go for it, you can make your own vacuum forming table big enough for RC car bodies and make your own body forms, like this guy: