Originally Posted by CSMRX7
With or without a harness bar if you put a car on its lid the roof will colapse. If you do not have the mobility to move as the roof colapses then your head and neck will take the brunt of it. When you flip a car with a normal 3 point the shoulder harness slackens allowing you to be pushed towards the floor of the car (now the roof). To my understanding the Rallye replicated the tightening affect of impact that a 3 point does, but not the ability to release upon roll.
I'm sure we can all come up with unique situations in which one design wins out over others, however, I still believe that a 4-point harness is safer than a 3 point in the majority of situations. Your point is valid, none-the-less. In a roll-over, with only an inch or two above one's helmet, even a slight collapse of the roof can have devastating consequences. I doubt, however, that a three point system is significantly safer in that situation.
I intend to have a pair of harnesses installed in my car before I take it to the track. I am sure that the majority of instructors are more comfortable with a four point than the stock belts. Four point belts also make it possible to utilize a Hans, which is safer still.