My thought was that maybe the rib on the back belt was in the groove of the SC but tolerances were a little off where the belt was slightly at a bind while in the rear pulley groove. Once it spins at higher RPM, friction increases causing stress and heat on the belt.

The hard thing about the interwebz, is a lot of the time you only hear the negative side of a product. I wanted to see if others have the same issue or if it's just me. I felt like I spent a lot of time troubleshooting this alone. If there's tons of people with the same pulley and they don't have the issue, let's put this very one someone's else's car for deductive reasoning!