Out here I do not know a club that will let you run with a 4 point harness. The six point Ed mentioned is the only good alternative for us at this time.
If you want to run, you must have the equipment to pass tech. If you don't buckle the sub-belt, most will never check. Check the rules for the club you run with. Anything beyond school level requires this. Time Trials, open track, etc.
Without a cage you are looking for the lesser of two evils. The sub is to keep you from sliding under the belts and wedging you under the dash. This rule was added for spine injuries as well. Pick your poison.
It works like this.
You spin....guy behind hits you in the door , fender, quarter
The guy in front of you spins ....You hit him with your front bumper
The guy following you has lesser brakes than you ...He hits you in the rear.
You ....spin, drift, miss a gear and hit a barrier or another car
Tracks are far safer than driving crazy on the streets IMO. Everyone is normally going the same direction.
The rolls I have seen, normally occur on fast sweeping turns, when the rear drifts or steps out and the driver gets scared, lifts off the gas causing a snap spin.
The spin does not cause it, sliding off the track with wheels crossed causes it.
"When in a spin both feet in, Wheel pointed straight" ...look at some interior race car pics and you will see a piece of tape at the top center of the steering wheel. Even the Pro drivers use this for reference on these occasions.
You are far more likely to see a mishap like the one pictured below. The driver is a 3 time T1 Regional champ and placed high in the Run-Offs. Considered a guy you want to be on the track with. He went for third and caught 1st. The Rear locked and snaped him into the barrier to his right at about 70mph. Now that's a bad day at the track. He was fine but his ego and wallet were not. The car has been re-built and running T1 again.