I typically represent the most militant conservative views re: rules allowances and I cut all of the spot-welded seat brackets out of my driver's side.

I'm not sure what a "hump" is, exactly, but to ME the distinction is between a bit that's welded to the tub for the purpose of mounting the seat ("bracket" etc., per the rule Greg noted) and the tub itself. I'd stop short of changing the shape of the tunnel, floor, sills, etc. within the allowances of that rule.

Intersesting however - I did NOT push to that extent on the passenger side. In hindsight, it's because i didn't really have a compelling reason (fitment of the seat) to worry about those brackets, but they could come out too. Heck - looking at the build pics now, I'm reminded that I actually REPLACED the main passenger side seat bracket. Funny how we think about things sometimes.

http://www.it2.evaluand.com/gti/build4.php

K