So, let me boil this down if I can.
I CAN: Mount an FIA seat to FIA side or bottom mounts (if the seat was tested with the ones I've selected) and bolt those to my sheet metal floor.

But I can NOT weld a cross car tube or box section or two from my roll cage to the tunnel (In IT) and attach with proper grade hardware recaro sliders that have been in use in Grand Am cup and ALMS for years?

IF that's correct, who's doing the logic tests for the ruleswriters?

yea yea yea, I know, "It's based on the advice of legal counsel".