Garret, wish I could help you with the back flange project; I've only got one, and it's in use! However, I would be very interested to know your opinion of the Rocky Mtn. flanges when you get them.
BTW, I wonder how difficult it would be to make the brass rings out of thin-wall copper or brass tubing of suitable diameter? I measured ¾" O.D. on mine. Such tubing is often available at hobby shops that sell brass shapes. Here's a quick google:
http://www.google.com/#q=brass+tubing+hobby
Here's another source:
http://www.amazon.com/Brass-Round-Tubin ... B000H9LB02 . Should be able to make a lot of rings out of that (it's 24" L)! See also
http://www.amazon.com/dp/B00564SIPE/ref=biss_dp_sa1
Of course, then you'd have to measure, drill, and solder in the "key," that little length of peg that locks into the goose neck. Not an impossible task if you have the tools.