There are absolutely no worries with using the ZO6 clutch/flywheel assembly with a TPIS spacer. I have 15K miles on such. You will need a spacer as the ZO6 assembly is narrower than the CTS-V. Both Ktech and TPIS sell the spacers.
The car feels 500 lb. lighter. It also feels like a 30 rwhp increase. Shifting is easier also. Installing the ZO6 assembly is a no-brainer. You are installing the assembly that was designed by GM for this motor. True, the car weighs 500 lb or so more, but the ZO6 clutch handles it nicely. The only clue to a technition that the car is modified is an enlargened hole in the bell housing for the clutch line.
Some people worry that the mass reduction will cause bogging or other problems in first gear starts in normal street driving. No worries on this. I routinely start in second gear on flat ground.
If you decide to do this, change your shifter at the same time.
As I understand it (and I may not be completely correct because I did not install the assembly myself), the hydrallic clutch line enters the bell housing through a hole that has lots of clearance. The clearance is there, in part, to serve as an exit for clutch dust. With the ZO6 clutch, the entire hydrallic slave cylinder moves towards the motor and the bell housing hole must be enlarged by about 0.75" to allow for the new location.