http://www.indplastic.com/index.cfm?fus ... roduct=303" onclick="window.open(this.href);return false;
.08 is generally what you'd use for a case. Looks in the case constructions sections of the forums and theres more infor on plastics.
Plexi I'm not too sure, I've never used it. And metal is all fine and dandy if you have the tools, skill, and dont mind the extra weight
Should be plenty. but I would get two just in case something gets messed up, that way you don't have to wait for more to ship in the middle of your project. Then you'll have extra for more projects.
You planning on vacuum forming or just straight edges?