That's nuts. If I had a Cobra and tracked it, I would invest in either a full roll cage or at least a better roll bar. I'd be too worried that single hoop would dig in and cause problems. When I got my Miata, the first thing I did was order a roll bar because after seeing crash photos with and without a roll bar installed, you'd be crazy not to install one
This is the page that won me over. The roll bar not only keeps your head from mashing into the ground, it also helps keep the passenger compartment from getting mashed up. http://www.bethania-garage.com/testimonials.htm
Clearly that roll bar helped keep that cobra driver safe. However, those single hoop roll bars still make me nervous