I tested mine in Buttonwillow yesterday. I was very impressed. I used to run Recaro with stock seat belt, and I can tell you this quick fit harness with stock seat is just as good as Recaro PP w/ stock belt. I loved how it felt under heavy braking
I bought the cheaper of the two (non-Hans) and it fits really well, I have no issues with lap belt tightening or anything else.
I am 6'0", 190 lbs