Just thought I'd post an update since I've finally got some miles on a 47C4572 C12 belt. The first consideration is that you'll need to open up the primary to get the appropriate clearance. I can't remember the exact measurements I took, plus I don't have a new 080 belt to compare with, but roughly speaking the C12 belt is around .040 wider than the 080 belt. It wouldn't touch bottom on my primary; can't remember what the clearance was with the old belt, but it wasn't tight. So you'll have to shim the primary in most cases. I had the primary serviced by Indy Specialties and sent the belt along with for them to set the clearance, and it checks at around .020.
Anyway, I'm pretty happy with the performance. I skimped on the break-in somewhat; I was a little rushed, so I just did two quick rides to heat cycle the belt before I loaded up to go ride. Hopefully that doesn't affect the belt life. It's not like I hammered on it when I got to riding anyway though. We'll see how the C12 lasts, but so far it "feels" great: smooth engagement, consistent response, and runs out well. I started with empty Magnum Force weights (60g), and added a couple grams. With that, it held pretty solid at 8000-8100 RPM up to 9000'. The 080 belt performed ok in my experience, but is more expensive and hasn't seemed very durable – the one that originally came with the sled was replaced when it nearly disintegrated, and the replacement belt has some cracking and signs of wear despite only a few hundred miles.
So far, I'd say it's a home run. Unfortunately, I never did hear back from Gates on why the dimensions don't match the 080 belt. I wouldn't think you can run the 47C4572 if you're not prepared to shim the primary, so plan accordingly. I can't remember what the 44C4553 was spec'd at, but that might be a better choice if you need something that'll drop in. In my case, I honestly can't see going back to Polaris belts unless the C12 doesn't hold up, and I don't think that's likely since I hear very few complaints on the newer sleds.