Have you considered running a proper, fixed backed, race seat with stock belts? Similar setup to a Porsche GT3 RS.

They hold you in place soo much better than just a harness if you have to choose. I have one in my race car and I really don't have to cinch the harness all that tight because the thigh bolster does its job.

A lot of people are focused on the upper body when its their thigh and hip area that provides the most feedback and needs the most support. Did you notice professional go karts don't even have harness installed? And they have higher corner loads than a car.

Just offering a safe and pratical daily driver solution.