Hi, we also made our own tank treads in CAD. (:
We just put up our website and blog as this is our first year in FTC, so here's the link to our blog post about the tank treads... (we do have the insert area in our cad model, and examples of them hooked up)
http://nanitesblog.blogspot.com/2010...ank-tread.html
We also plan on making the inserts soon. (:
At our website, we also plan on putting up more CAD models for all the rest of the "missing pieces" from the kit of parts.