[shawnz]

Note that the maximum centre of mass you can have before tipping (assuming CoM is in the middle of the bot) is (wheel base)/(2*tan(max angle)). So, if your wheel base is 11", and the greatest angle you'll see is ~21degrees (going over the bump, arcsin(4/11)) you won't be able to put your CoM any higher than about 14" off the ground without fear of tipping! Of course, the bump is specific to this year -- but keep it in mind.

On the note of turning performance, we were highly recommended against using 4WD with all solid (non-omni) wheels -- but at a wheelbase of 17", we haven't noticed any issues. It does skip while turning of course, but not enough for the drivers to be able to notice; especially on carpet. All in all it has been very successful for us so far.