[Andrew Schreiber]

Tread? What type, how is it held on?

I assume you are CNC-ing this. (how does one turn CNC into a verb? PM me) Do the small holes near the edge of the wheel really remove that much weight? I can't imagine they do, Try seeing how much it takes out. I know that they look cool but they probably increase your manufacturing time by a lot. Otherwise you could just drop a piece of 4" round 6061 on the lathe and have this wheel knocked out relatively quickly.