I'll check him out, don't know what type of alloy he has though, its listed as grade EN485, but that's not a grade I ever heard of...
Chains and sprocket is a good idea, as you mentioned weight will be an issue, but its an other option.

Bumped into this website by chance, dont know if anyone ever bought something from them, it looks interesting, they even have a complete track drive system, and its not expensive at all...my only concern is its plastic!
http://www.vexrobotics.com/vex/produ.../276-2168.html