We've always used aluminum from the AndyMarks manufacturers. It is a bit heavier than say, fiberglass or polycarbonate, but it's strong and is especially good for first-timers, because it's pretty easy to work with. Here's what we always use:
http://www.andymark.com/ProductDetai...Code=am%2D0202
It's nice because the holes for nuts and bolts and whatnot are already there, and it's easy to cut with a basic cutter.
Hope this helps! Good luck from team 3397!
