I like 12" cube rule, firstly because I have 7 sets of parts
for a 12 x 8 3lb hockey bot

but also because it will make
Design of shooters much easier.......
I would also think some sort of wedge rule (like those in the nerc sportsman class) might be helpful so that it does not just become a contest of who has the lowest wedge.
How about "any part of the bot , other than the wheels, that touches or comes within 1/8" of the floor shall be vertical for a distance of 1/2" inch or be otherwise designed so that it does not act as a wedge to get under opponents bots.