[EricH]

I also am concerned about the omnis. I worked at a go-kart track for three summers. The amount of sideways sliding around that that base is doing is something that we wouldn't allow except maybe on the slick track, and probably not even then--it looks like you have no control sideways, and on the slick track you did have some control even when going sideways (you're effectively trying to drift at those times).

What I would do, if you were going to have a person riding it, is to figure out which end will be the back. That end would get 2+ CIMs/wheel, and some form of traction wheels. (Personally, I'd throw some Colsons on as traction wheels--they aren't that hard to adapt to an AM parts set.) The other end would get some weights, and dual omnis to smooth out the ride.

The other option I might pull would be to utilize mecanum wheels. For example, the AM 10" ones. This would give you side-to-side control, with some ability to slide around--and I'd go with a pair of CIMs on each wheel.