Racing seatbelts should not be used in a car without a rollbar. PERIOD
In the event of a rollover collision the roof can collapse killing the occupant if they are firmly held in place with a 4 or 5 point harness.
Most sanctioning bodies do not allow the use of harnesses without adequate rollover protection.
If you ask yourself what are the chances of this happening my friend rolled over an immaculate 360 duster this past summer when it spun at 115mph at the drag strip.
The roof was crushed down to the steering wheel.
Fortunately for him he was wearing the factory belt and his upper body ended up between the front seats.
I also read somewhere that if you bolt them to the floor it somehow puts the wrong angle of restraint on the body, possibly breaking your back. (front end collision)
I also read somewhere that if you bolt them to the floor it somehow puts the wrong angle of restraint on the body, possibly breaking your back. (front end collision)