It is about the robot's length horizontally.
If you are, say climbing the tower and are tilted up(example:
http://i.imgur.com/lAv10.jpg) , you are still judged on you horizontal length, not you robot length. So you could have say, a claw that extends out, and increases the total length of the robot (diagonally) past 54 inches, but still remain under 54 inches measured horizontally, would you get penalized for having a robot longer than 54 inches.
I say no, you are within 54 inches horizontally, my teammates say yes, your length is over 54 inches, no matter the orientation of the robot. What says Delphi?