Yeah, I have to look at tires too. The rear tires on the '09 Z are getting pretty long in the tooth now. And the tires on the C5Z aren't much better.
I actually would like to put runflats on the C5Z, but last time I looked I couldn't find anything like that available. Non-runflats are a better ride, but living out in the boonies, if I get a hole punched in one (like happened with Connie's 2007 C6), I'm pretty much screwed. No one nearby will have them in stock or even able to get them in a few hours. Heck, for that matter, probably most areas of the country would be the same situation for getting a quick tire replacement. So a flat tire is going to mean spending at least a night where ever you are.
At least with runflats, I could get somewhere under my own steam instead of being dead in the water at the side of the road somewhere.