They mentioned the C5 Z06 version has worse aero than the base model. Yup, it was not originally designed to be the fast version. The C5R roadracers used the normal C5 Fastback body, not the Z06 design.
What happened? GM wanted to make a budget version of it's new C5 Corvette. They called it the FRC (Fixed Roof Coupe), and it can be identified by a having a flat rear deck where the trunk is, whereas the fastback is sloped. Well, the stripper FRC didn't sell very well. Rather than abandon it, GM came up with the idea of turning it into racing version. Because GM has a hard time with original thought, they regurgitated the Z06 option code (all GM option codes are 3 letters/numbers, Z28/PYO/MN6/Z06, etc) which was originally used on the 1963? model to specify disc / metal brake pads, IIRC. The first Z06 cars weren't called Z06's, it was an obscure option code that wasn't intended for street use. With the new Z06, you got a 3080lb empty hardtop with a rear transaxle giving about 52%/48% front to rear bias. It came with a 6 speed manual that rattles, and the trans tunnel get hot when you're racing. No T-top or convertible. No spare tire, just a can of seal-n-air and directions on how to hitchhike. Memory seats and museum delivery were the only two options available when I bought ours. It comes with a video tape describing how to adjust the car for racing among other topics. First version was the 2001 at 385HP, then 405HP from 2002 to 2004.
Notice the C6 gets less aero than the C5. GM decided that styling would play a larger role in the C6 than it did in the C5, and there are several things done for looks that hurt the cars performance.