Beware of having a roll bar or cage in a daily driven car. In a wreck, you will put yourself and any passenger(s) at risk. You really don't need one for auto-x. The moment you put a roll bar in you car, you are restricting yourself to 2 passengers.
Even if you are building a track car, once that track car will be daily driven, you don't need to have a cage or bar in it neccessarily.
I had a roll bar in my old car and when I got into a wreck; even though I was belted up and using an e30 euro recaro seats with bolsters, I was not held in well with the standard seat belt. On impact ( car slid backwards into a median ) my head made contact with the diagonal bar, split the foam padding, and the hat I was wearing which had a metal buckle, proceeded to slice my scalp :eek:
13 or so staples and a concussion later I was glad to be alive. A few days later I yanked the roll bar out and sold it. I will never use one unless I have a harnesses, helmet, highest density padding and a race seat as that's the only way you are safe.
Granted I have seen cases where people have been saved by roll bars/cages on the track, for a street driven car, it provides more harm than danger.
My 2 pfennings.
