thats what I have been doing. Shaping a peice of foam then making a fiberglass casting of it. I would love to do the pulled vacuum form plastic but I cant seem to get any success with the attempts I have tried. I tried making a vacuum box with holes in the top and a hole for the vaccume hose on the side but when I put the heated platic from the oven on it, It just didnt seem to want to shrink around the mold very well. I think the plastic was cooling too fast after I took it out of the oven because it stiffens right up as soon as its out of the heat.

The article you posted looks very interesting to me. I might have to give that a try.