[Perfectlap]

well I don't about your area but here we have half a dozen different clubs some regional some national like PCA and SCCA. They all have differing rules and enforce the rules differently.
I did see someone fit 6 point belts to a stock 996 seat once, I think pics were on Renntech at one point.
Then there's the CG Lock which I've used, just a fastener that keeps the stock seat belt from coming loose at the lap. Very effective for a few bucks.

If you like Autocross and are going to venture onto the track investing in a GT3 seat or Recaro Pole Position, which bolts right into the existing floorboard holes-no need for an extra set of rails,
is a good investement.