We're in very much the same boat as you guys...
We're going ahead with the CVT, despite my loud protests. It was my idea in the first place, but I was only kidding, and now our uber-fabricators are getting carried-away and... *ahem*
The current plan is to build the KillerBee's Transmission (FIRSTwiki:
Four Speed Transmission), as a fail-safe in the (IMHO) likely event that the CVT doesn't pan out. The killerbees tranny is probably your best bet, and they will be posting a white paper "any time now" (though a gentle reminder may be in order). The easiest way to get a sweet tranny, but forfeit your rights to any kudos because you are a talentless hack, is to buy one. You can get a DeWalt drill and remove its gearbox system.
If you want to plow through with a CVT, I've written a qausi-informative article on FIRSTwiki that includes a rendering of our design. A CVT will be heavy beyond reason and you'll also need a differential unless you want TWO CVTs. You are really opening a can-o-worms if you take on this project...
Don't say I didn't warn you: (FIRSTwiki:
CVT)