When I got my Methods put on, at a very reputable chain around here, the guy came back to me 1/2 way into install and said that I needed rings to make the wheels hub centric. He thought he might have some the size I needed but didn't, called their supplier and they didn't even make that size. Then he even called Method directly and spoke to someone. The guy at Method said that there is nothing to fit and that everyone runs them without a ring. When the install guy told me this, I made sure to ask him if he also thought it was ok. He said yeah, the ring is a small detail thing. And like someone said above, he said that if the wheels are mounted right and torqued correctly, no one would be able to tell any difference.
Hope that helps. I've been VERY happy with my Methods and I haven't heard anyone who got them and didn't agree. I was slightly concerned too when the guy said they should have these rings but couldn't find them, but my experience is that the difference (if any) is unnoticeable.