Check this post by Shazaam. I thought it was very helpful to decide which size to use. http://www.ducati.ms/forums/showthread.php?t=64489
I just added 2 teeth to my rear sprocket yesterday. With FatDuc O2 manipulator, and 15t/41t sprocket, along with a 525 DID chain, the bike is running great!!! It has a very smooth ride, and seems a lot easier/faster to lean! Maybe cause the wheelbase just got shorter by 8mm?
Anyway, I got them from sprocket center. Watch out though. The reason why I didn't change the front is because they sent me a monster 14t sprocket, which doesn't fit the SC... I'm planning to call them soon to replace it.