The cage in his Camaro doesnt have to meet federal safety standards, its in there for 1/4 mile track standards, which most likely are stricter than federal hoopla. Judging from the fact he took it on the HotRod thing. That and tracks dont play games with fast cars and lack of cages.
A single bar over your head will keep the most important part of the cab from being crushed, ie the part over your brain bucket. Now, a complete cage, much like a 10.5 Outlaw car, would be much much much better, but a single bar will be much better than factory sheetmetal. Seriously though, it takes a pretty big hit to completely crush a cab in to the point of crushing you. A simple slow speed roll over wont crush the cab flat with the dashboard. Now, falling off a cliff onto your lid will most likely do some serious damage. So you must decide how much your wheeling requires how much cage you need. A rear bar, with halo over your head and running down A-pillar to floor pan would be ideal, but if thats alot of work for you, I would just run the overhead bar, make it thick, and call it legit.