I find it interesting that this post has turned into a post on acrylic vs polycarbonate.
With students, I normally do the "vise test" . .
Give a student (with safety glasses of course) a small piece of polycarb and tell them to smack it against the vise.
Then give them a piece of acrylic and tell them to do the same thing.
That'll teach em.
(and yes, you need to put your numbers on your bumpers . . silver Sharpie works GREAT!
http://www.amazon.com/Sharpie-MARKER.../dp/B001GXFNYI)