so my actual ring measurements ended up being 64.85mm OD x 56.55mm ID. After thinking about it further I don't think that the rings are actually responsible for 'transmitting force to the hub' like some people say... all the rings I've found are either plastic or aluminum, which are easily deformed materials. If they were actually handling much load I think they would need to be made out of a much stronger material.
Having said that, I do think they are necessary to properly center the wheel on the hub, and they are necessary to make sure that the bore of the wheel is concentric to the bearing when you tighten the wheel down.