I know the ideal is a seat made from a garbage bag filled with a little two part expanding foam and seat belt mounts welded directly in to the cage at the dimensions specified in the seat belt instructions or FIA/SCCA manual. That works great in a space frame race car where the seat area is built with maybe 1/2" clearance for the driver. If you do it right you've got to worry about the rules for exiting your car in a certain amount of time.
In a caged car, usually you want a fixed back seat with a seat back mount going back to the harness bar and the bar placed right for the harness.
Then there is the same idea with a roll bar instead of a cage.
Then there is a huge gap in the effectiveness between a roll bar and the topic of this thread.
A well designed hoop with harness bar would fit in that gap and work for a lot of people who won't get a full roll bar. It just makes sense.
In a caged car, usually you want a fixed back seat with a seat back mount going back to the harness bar and the bar placed right for the harness.
Then there is the same idea with a roll bar instead of a cage.
Then there is a huge gap in the effectiveness between a roll bar and the topic of this thread.
A well designed hoop with harness bar would fit in that gap and work for a lot of people who won't get a full roll bar. It just makes sense.