Thanks.
Unfortunately there aren't any videos with the ball in the gripper, although I do have one picture (albeit it crappy) of the robot holding the ball in the air, just low enough to drive underneath the overpass while popping the ball over, and not having to stop.
We ended up using four of the Igus bearings, two on the outside, two on the inside. The combined support of the 4 of them has worked out pretty well, no problems that I know about.
Of course, we discovered the differential in the Aim High game when we were prototyping this same bot, although we never built it. It's from Northern Tools, it's a bit heavy, but it is very strong, and we lightened it substantially after we had the axles lathed from 1" to 5/8".
http://www2.northerntool.com/product/35768.htm
And here are some pictures to go along with that:
-Greg P.