Is that a brand name for polystyrene? If so, I used that for all of my hard parts, including the helmet. It was great for everything except the helmet - It only curves along one plane so it is nigh impossible to get the correct shape. Pics here: http://kimncris.com/costumes/zam.php
It is a great light-weight alternative for those whose accuracy standards are a bit lower, including myself. I use polystyrene for lots and lots of stuff. Well, at least I used to when I actually had time to make costumes and props!