<R06>

[JackG]

Let me quote <R06> so that we have some reference here.

ROBOTs must use ROVER WHEELS (as supplied in the 2009 Kit Of Parts and/or their
equivalent as provided by the supplying vendor) to provide traction between the ROBOT and
the ARENA. Any number of ROVER WHEELS may be used. The ROVER WHEELS must
be used in a “normal” orientation (i.e. with the tread of the wheel in contact with the ground,
with the axis of rotation parallel to the ground and penetrating the wheel hub). No other
forms of traction devices (wheels, tracks, legs, or other devices intended to provide traction)
are permitted. The surface tread of the ROVER WHEELS may not be modified except
through normal wear-and-tear. Specifically, the addition of cleats, studs, carved treads,
alterations to the wheel profile, high-traction surface treatments, adhesive coatings, abrasive
materials, and/or other attachments are prohibited. The intent of this rule is that the ROVER
WHEELS be used in as close to their “out of the box” condition as possible, to provide the
intended low-friction dynamic performance during the game

This rule says nothing about normal force, gravity, or anything like that. The only time normal force was mentioned (at least so far and to my knowledge) was on Bill's blog. He discouraged teams from making devices specifically designed for increasing normal force. I'm sure the GDC is reasonable enough to realise that increasing normal force may be a byproduct of certain robot actions and thus would not outlaw them.