I am not saying this is the best - But I have an OFNA Hyper 7 PBS RTR - The starter box that came with it sucked so I sold it on EBay and bought a better starter box.

I love the buggy. It is a single speed with no 2 spd available for it. But IMO you do not need a 2 spd on a buggy if you plan on racing. I have done 30 - 40 ft jumps so far.

As for ground clearance, mine is maybe 1/2 inch off the ground if that. They have flat bottoms so you do not get hung up on anything.

I am trying to construct something so I can jump the swing set in my yard, but I do not have enough running room to get the speed I need.

Hope this helps.