[Rizner]

One reason the GDC may not want others to expand when touching the opponents tower is that they could build a giant wall and just go back and forth blocking balls that are being shot from midfield. You could easily build a robot that contacts the tower at all times and expands to its Finale Configuration (84" by 90") with a giant wall. This gives a little over 4.7 feet (56.5 inches) of a clearance window on the side it's covering, and if it's set up driving parallel to the bump it could probably maneuver from side to side pretty quickly.

This is just my thinking, though.