Harness bar mounting question

[illwillem]

Im in the market for a harness bar (Dali, SOS, TI Dave, I's impact, Mugen, comptech etc) and had a question about the lower mounting points. I know the bottom typically bolts directly into the rear threaded seat provision, my question is does the seat then sit on top of the harness bar- or does the seat bracket get sandwiched between the floor and harness bar. Im rather tall and and aiming to get every last quarter inch of headroom out of my seats as possible. I see how some of the bottom mounts of the harness bars are stepped, just wanted to double check how they are fitted with people that have one.

This set up will go with my Recaro Hans pro racer and buddy club rails with custom 'L' brackets to lower the more than with the ones that come with the BuddyClub.
thanks