Take a look at the discussion here:
http://www.chiefdelphi.com/forums/sh...threadid=16025
The only reason to not build a robot that go under the bar is that 14" is really small to fit under, and some of your ability might be limited if you choose to build a robot that small.
The top of ramp is so slipery and huge that most robot should be able to pass through it during matches.
I have a feeling some would rather stack up 15 bins than go under the bar, or have the ability to protect a stack with the whole robot.