I'd very strongly recommend you upgrade from the 4 point harness to a 5 or 6 point setup. Schroth is the only company I'd trust 4 points from, and even then they're not as good as a 5/6 point setup, especially since you already have aftermarket seats, no reason to not have a sub belt imo.
No question 5 points much better. I have the Schroth 4pts for now. The Recaro Sporster isn't ported for that 5th belt so I would have to replace the seats.
While I am happy this thing is up and running I am suffering from project fatigue. Right now I just feel like selling it but that feeling will pass so I am just going to let it sit for a little bit and decide if I go the rest of the distance and purchase a truck and trailer.