I remember reading a post somewhere where a guy was building a large enterprise for vacuforming, and had done so by: a) scaling up a paper model b) filling in the inner cavities of the paper model with expanding foam (in effect making it solid. c) covering the outside with bondo and then sanding it down. Sounds like a great idea, but my worry would be the expanding foam, which to my knowledge is quite a dangerous substance, especially if you were to inadvertently start sanding it. So the question is - does anyone know of any safer alternative(s) that would do the same job? Thanks in advance Paul.