I think that that should be allowed the full weight advantage. You would need it to make it effective. I think as long as the foot doesn't spin 360 degrees like a wheel (or an off centred one) i think shufflers are only shufflers if they rest on some static feet (or the base of the robot) during some point in the walking gate. I would have thought that even if you put a foot that is kept vertical (ish) and then is moved in a circular motion by a crank should be alowed. As long as it has enough of them so it doesn't rest on its base. What do other people think? Because I think there should be more unique designs.