[angusp]

Well I like the sound of getting another one...

By side-side motion I'm guessing you mean a tipping force - and the the answer would be that he's pretty hard to shove over, at the limit of his lean he's stable, 10 degrees tilt and he'll fall. From fully upright, you need a bit more of a shove - having just pushed one over. Sandy says they can tip themselves if you wobble fast enough.

We're guessing you were thinking of something like this --> http://i.imgur.com/Cmmwu5A.jpg

[asimuvPR]

Yes, exactly. This platform is very affordable and would make a great introduction to a sumo-type robot competition using bipeds. But not shoving robots around a la RoboOne, but hitting a target drawn on a touchscreen. Its something Ive been tinkering about for a while.

I appreciate the answers. Best of luck with the project!