I have the Brey Krause bar in the Z06 and it works out very well. You can use the stock seat belts and the harness at the same time or separately. It utilizes a 6 point system rather than a five point, but you could fabricate a plate like JR's and make it a 5 point. Quality is excellent and you only have to make a small slit in the plastic near the outer seat belt attachment for the mounting point. Here in
Detroit we do not get many chances to ORR, but we run a number of low speed and high speed time trials and you are held in snugly. I even took an off course excursion into the tire wall at one track and did not noticeably move--not aches or pains.