My 05 front GY RT/S tires showed signs of cupping @ approx 5K miles. I ran them until 10K and they were definatley undoubtly cupping. I removed the OEM shocks and rotated the front to the back @ that point and as far as I can tell, the tires are "evened out" and appearing as normal @ 24K miles.
Dave S.
Edited to say...
@ approximately 20K miles, I added the EE rear swaybar. Although it helped out the rear end, I don't believe it had had anything to do with the corretion to my front tire cupping problem.