Yeah, I agree that my K10 seems a bit loose fitting; it's certainly easier to slide in and out as compared to my other CIEMs. However, the stem is about 25-30% longer, and this somehow contributes to a better seal.
Probably should have sent them in for a refit, but was too excited to let them go! Anyway, they're very comfortable when I sit up and listen, but when I recline, my ear canal changes somewhat and they become a little more loose. Don't know if Noble will refit after the 30 day window?