pic: Captain Whidbey's Proswishper is walking down the stairs!

[RunawayEngineer]

I'm happy to see a battery counterbalance. When I saw the CoG issues that were going to come up, a shifting battery was one of the first things I thought of - but I wasn't sure that a team would take the risk of making their robot's heart mobile.
I would have thought that this approach would be most beneficial to a team going for a 6 stack since that is the worst case scenario for CoG shift. Is it to address the issue of tipping, or is it to distribute weight on the wheels? How significantly does it control CoG?