Thank you Brian,
I messed up on the adapter, as you noted. What I did was turned down the brass adapter to the exact thickness of the tube. Didn't think about it then, but realized (too late) that I didn't leave enough material to sand off and remove the cutting marks all the way.
Rookie mistake. I couldn't sand off any further because the diameter of the clip was exactly the same diameter, so if I took any more off it wouldn't have been right.
I wanted to carve lines around the adapter, thereby disguising the marks, but as soon as I showed it to it's new owner, he was taking it immediately! I showed the flaw to him, and he wasn't leaving without it.
The camera magnifies it significantly, and it really is barely noticeable unless you know it's there.
He is a personal friend, so I can get it from him any time and fix it though. Maybe after a while he will let it go!