To take this in a slightly different direction, I have had additional thoughts on the potential hazards of hearing a harness on the street. My thoughts involve not rollover protection, but rather frontal-impact protection.
In a front impact in a normal 3 point belt, the upper body is able to move forward a bit, and the right shoulder is able to rotate forward and around due to not being restrained. The head and neck will naturally snap forward during this impact, and because of the forward-leaning angle of the shoulders, would impart more of a "pulling" force on the neck. Your head and upper body then coem to rest against the airbag.
Now imagine the same crash in a tight harness- you've heard the whole Dale Earnhardt story- in that same crash, your shoulders would stay planted in the seat back, and your head would snap forward, but at a more acute angle to your upper body. (Typical basilar skull fracture thing). You would probably never even reach the airbag, depending on how close you sit to the wheel.
So I have come to the conclusion that unless you wear head and neck protection and the necessary helmet, it is more dangerous to wear a harness than not in a front impact. I've read a lot of stories about people drifting into oncoming traffic, and there is not much time to react.
Any thoughts? Am I mistaken, or overly worried?