This is a close-up of the six-point anti-submarine belt attachment. Itbolts to the outside of the lap belt mount on each side.
The shoulder belts must not depend on the seat hole for their verticallocation. There should be a seat mount bar or chassis bar behind theseat that locates the height of the belts coming off the driver'sshoulders. The bar should allow belt angles of about 10 degrees downbehind the seat.
Most of us are familiar with the five-point harness; it has a single,front anti-submarine strap attaching below the seat. This isn't bad.I've used one for years, and my voice is still in the same range it hasbeen in since I survived puberty. The purpose of the strap is not tokeep you from sliding forward, but to keep the lap belt from riding upand then letting you slide forward.
The six-point harness has a double strap, if this makes you feel better.The best part--it's easier to mount than a five-point setup. The doublestraps attach to the lap belt mounts. Then they wrap under the seat andgo up through the front hole in the seat.
A bottom view of the seat shows the two anti-submarine straps routedunder the seat and attached on each side at the lap beltlocation. The tab in the center is for attaching a five-point harness.This tab should point down or back, not forward or up.
Conclusions
Take time to properly position a seat; use a mounting that attaches inthree places to the rollcage; pick a seat that fits properly; use thecorrect brackets; and finally, use care in selecting belt mountingpoints.