For the Recaro Profi XL floor mounted, I have mine on the BK R-9075 and 9076 side mounts on the 9044 floor mount with integrated sub bar. Those side mounts have a built in seat belt receptacle adapter. I have the rear mounting hole of the side mount over the rear hole of the floor mount, secured by the bolt that holds the seat to the floor. I got this idea from calling BK, they are great to talk to, and gives me lots of leg and headroom. I love it! Only hassle is when I need to take the firewall cover off as it is very tight. Also nobody can drive the car but me since the seat doesn't adjust
I also had it on a recaro slider for awhile which was good for street driving but going to floor mount gave me a little more leg and headroom.