That really is variable. I wrote the code so that the ramp step can be adjusted. So, number of steps = 128/StepSize. Time between steps should be about 150-200ms. I dont have firm answers yet because I am still working on the mechanical aspects of the robot.
Try to picture this in your head... hope this description is not too horrid.
The robot body is one of those large rat balls (Put the rat in, it rolls around the floor). There is an axel through the middle and a motor on the axel drives the ball. Most the electronics and battery reside on a tray that swings left and right to provide steering. There is a support arm that forms an arc across the top and on top of that are a number of sensors. The support arm is fixed to the axel, and the tray with electronics provides counter weight to keep the arm upright. Too much acceleration will either cause the sensor arm to crash into the floor, or cause the bot to swing wildly.