Bring lots of spare parts if you feel that your robot is vulnerable to damage if tipped over.
At Alamo Regional (San Antonio,Texas) this weekend, we saw some "rough play" where a robot was pushed over by one from the opposing alliance. I do not recall any Red-Cards being given for that in the second match of the Finals. Most of the tip-overs we saw were "friendly fire" the result unsuccessful bridge balancing (co-opertition and with alliance-mates). My observations agree with ToddF's in his thread discussing bridge balancing strategies (
http://www.chiefdelphi.com/forums/sh....php?t=104101). I seem to remember a few where the only robot on the bridge lost control and slipped over the side.