[JesseK]

We have had this problem as well in the two years we've done a 6WD. Even in '08, when the front wheels were omni and and two rear traction wheels were spaced only 12" from each other, we still had issues ('07 was a rocker). Come to think of it, our ramps were mounted on the outside of the frame in '07 and the mass of our elevator in '08 came down right on the inside of each wheel.

This makes me wonder if the mass distribution left to right on the bot should look fairly centric rather than outward.