both - actually. I have the radius at the base of the tunnel sliced to allow said frame, and do use the brackets to seat before seat into car assembly order.

the seat is rediculously low this way, the 1" of framing added tot he car puts the seat bracket bases lower than the stock seat mounts and the seat is low in those brackets. I can just barely squeeze my skinny arms under the seat from about halfwat back, not enough to do anything but grab belt webbing and the like. I'm 6'4", mostly legs and arms but still have a longer than average torso, and with helmet I have 4-5" of headroom in an AW11 MR2.