The C5/6 platform construction utilises the same process - but as you state, is a different shape. Hydroforming (bending tubular aluminium structures that are filled with water to stop them kinking) has made the 'chassis' incredibly rigid - far more so than was ever achieved with C4 and in the race car, stiffer even than the 550/575 racer.
The C6R is shorter, has a slightly increased wheelbase and is also wider than the C5.
My understanding is that the ZLT1 7.0 litre motor, transmission, cooling, suspension, brakes, steering and fuel delivery systems all carry over from the C5R - which is not great news for GTS competition.
The car as tested at Road America - is lighter than it's predecessor too.
There is a public test/shakedown at Sebring weekend after next. Corvette Club of America members get (chaperoned) garage access, so I'll report back on my findings. My understanding is that Pratt & Miller are not too phased by the DBR9 at this point in proceedings.....