[Bongle]

Just thinking more about ramps, you could help with a lot of the tipping and space issues by making a bent ramp so that it greatly increased the amount of flat space to drive onto.

The attached one would have a 2 foot long flat section, then a 3 foot ramp section that climbed at 18-degrees to a height of 12 inches. The total amount of flat space would be 3 feet wide (maximum length of robot) and 4 feet long (2 feet on the ramp + maximum width of robot). Mechanically all you'd need is a tiny latch on your manipulator arm (presumably on the left side of the shown robot) and maybe a tiny pusher to get the ramp to fall down. Problem with this is that you're now limited to a 100lb robot that needs these two huge towers on it, and has to be built to support other 120lb robots. I'm not an mechanical engineer, but it seems that this design of ramp could be built pretty lightly if you were creative with materials.

If you put some vertical posts on the underside of the ramp that had really grippy feet, you might remove the robot-shaking issue when mounting as well.