[steelerborn]

We are thinking about doing a mecanum drive this year as well, and we have no experience with them in the past. I would say to use the standard toughbox that you guys were using, and see how the speed of your robot looks when built. If you would like even more speed AndyMark has several gearing options for the toughbox that would be just a simple gear change (but you need to design your bot to have easy access to the transmissions).

Hope this helps.