I am trying to design and market a bolt in rollbar. The joint in the link is the strongest one I can find and I am waiting for info from NHRA about certification when using that part, so the bar can be broken down for ease of installation/removal.
I know an engine builder and chassis guy in the Northeast that works on some very competitive F.A.S.T Racing Cars and he says they mod the cages to be bolt together (not welded and bolted in place) and says they cover the joints with roll bar padding and it flys.