Im not sure youre going to get what you think.
Foamalux is a rigid plastic which has smooth faces. It's 100% PVC plastic rather than being EVA type foam coated in PVC. It's what they tend to make things like shop signage from. Im not sure that it will be quite as 'foamy' as you imagine. It will bend along a straight line if you heat it with a heat gun, but you wont be able to do compound curves with it, and when it cools it tends to try and return back to it's original shape unless held until totally cool. You also have to heat it to a point where the plastic is almost melting to do that, so you cant really hold it unless you wear gloves.
I used Foamalux to make blanking plates and other random parts for my track-day car a few years ago so I do have some experience with it.
Still, it's actually a really useful product, easy to work with and cut, and will probably come in useful for a few things whatever you end up using it for!
