i had tires cup at 4500 mi. Dealer did an alignment and refused to replace the tire. Some people have had luck getting the tire replaced, but most others have not. I just went ahead and bought a whole new set of Michelins and now BFG's and haven't had cupping since....so my ST wasn't the reason (i've gone about 20,000 mi. on the different tires), the crappy tires might be. Good luck!! I feel your pain.
One last thing, if you read your warranty, I believe tires are no longer covered after 12,000 miles if I remember correctly. I remember mine started cupping at 4500 miles, they just rotated them and told me they "fixed" the problem (I was stupid and believed them) and then they started cupping again at 12,500 and they then refused me a replacement due to warranty restrictions. Oh well...my BFG's are 1000 times better.