Watch TOG's link to the Speed Report. The Speed Report was surprising and Robby said this year's Hummer is all Carbon Fiber to keep the weight down. As carbon fiber is a exotic manufacturing process requiring autoclaving parts once they are laid up, it makes one wonder who he is working with - Lockeed or one of the other aerospace boys or prehaps one of the Indy Car or exotic car chassis manufacturers for Rolex or other series. While the stuff is super strong, it does not bend but breaks.
His test program is running the hell out of Hummer and then every 500 miles rebuilding it. As of Homestead, he implied they would run a couple of cycles before they ship the cars south.