Moved to appropriate forum

At least a few have gone to 18" all around, but not so much to rotate tires. Personally, I see no reason to rotate tires on a car that gets, at most, 18 to 22 thousand miles on a set of tires, and neither did the manufacturer.

Also, your tires are likely unidirectional, so to rotate you are going to be moving tires from wheel to wheel - seems like asking for trouble to me.

You bought a sports car, not a grocery getter or work truck. I"ve had three roadsters over twelve years, I've never rotated tires. If I drive like my grandmother would, I can get 30,000 or so miles on a set.
The way I drive it, I get 12,000 to 18,000. By the time I am down to wear marks, yes, the tires wear unevenly, but not enough that rotation will deliver more than maybe 3000 more miles. I rotate my truck's tires, but not the Crossfires.