I have a question. And I may just be stiring up useless conversation, from the usual crowd, but I think it's valid.
Even with Provo's setup. Which by the way look shmick, easy to use, and functional. What would happen if you were wearing a harness, hit a tree/car/pole from the passenger side and the car began to stretch around pole and become bananna shaped. You would be at risk of the harness seriously stretching, and I imagine that your body would be the weakest link. This bar wouldn't move, and the bottom ADR eyelets wouldn't move, but the distance between these two points would increase. I can imagine this would almost be a fatal situation, crushing your upper body, neck, shoulders, lungs etc.
Now I know this wouldn't be as likely to happen with a full cage, as the car wouldn't bend. But are there any other ways of preventing this situation? Because while harnesses have their merit in rollovers, as apposed to a lap sash. I would imagine that a lap sash would be better in this situation, if the car was without a cage.