This project started off with it being a one piece deal. However, a broken drill bit deep in the hole caused me to change plans. I tried removing the errant piece chemically, but that didn't work, as the simmering chemical (alum) would get stale quickly in the deep hole. Long story here. Anyhow, I cut the split ring off and made one that's a light push fit over the camera end of the adapter - smaller end. I'll Locktite it lightly when I'm satisfied with everything.

The circular slot that makes clamping possible is 1/16" wide and covers more than ½ the circumference. I normally us a slitting saw for this type of operation, but this time I just mounted the part in the 4-jaw and offset eccentrically about a ¼", and used a parting tool to cut it. The cross slit was made with a .032" slitting saw. I bored the inside of the adapter large enough so that a wrap of electrical tape around the eyepiece is required to snug things up. This way, the eyepiece's finish is protected.