Materials for test, foam?

I have been a member for a bit, and have learned a lot from the
archived messages. I have my 30"yx40"xx4"z cnc gantry functioning
well in wood--but I am looking for something I can cut to test paterns
(topographical models) before committing to an hours long, multi tool
cut that might not come out perfect. I seem to recal there being some
sort of dense beige foam--I am thinking that I could cut this at a
higher speed as a test. Does anyone have any suggestions as a
material? --this is probably just on the edge of being off topic, so
if you can suggest another place to ask the question it would be most
welcome.
Thanks,

Peter,