Building anything useful out of NURBS curves in maya is like gouging your eyes out very slowly while doing mathematical calculations. Yes, they’re great to mock up a car very quickly, but you should leave it at that and convert to polys/sub’ds as soon as possible. For one of the projects this quarter, I had to model a medium-res car ENTIRELY out of NURBS surfaces. It was one of the most frustrating things I’ve experienced, and wasn’t helped by the fact that my car isn’t very curvy to begin with. I wasn’t going to post it anywhere because, frankly, it’s not very good, but perhaps there’s some maya users out there who understand.