[ALIBI]

If you are concerned about giving up possession of the TrackBall, why not have your robot pass the TB over the overpass and pull it back? From the Q and A:

"A robot may break all contact with the Trackball as it passes over the Overpass. Likewise, a robot may be in contact with the Trackball when it passes over the Overpass. Either would be considered a valid Hurdle."

I can think of four or five ways to do this (or something similar). Of course, since the kids have only decided on their drivetrain at this point, I must keep those ideas to myself for now.