Just a note to say that I use a 62mm adapter for my EM-140 ring flash and 105 Micro f/2.8 AF-D Nikkor. It fits at the far end of the fixed barrel.
The advantage is that it takes the weight off of the extending end of the barrel and the associated focusing cams. I believe the Nikon R1 system will do the same and with the R1 this would be particularly beneficial and allow for more lights (and weight) on the adapter.
Along with that, the lights are further back from the subject, somewhat lessening the light angle. That could be good or bad depending on what you are trying to do but having both rings allows for some minor adjustment of the light angle, not otherwise possible.
The 62mm adapter also allows you to put about as much torque on the ring as you want, should it stick, without worrying about damaging the cams