I have had my Contender for three years and locked full time. It is a fine cage and the workmanship is of a quality rarely seen anymore. The only minor annoyance has been the cage rotating and the lock getting uncomfortable. I still have my original Chinese cage that I started with. I remembered it having a different ring design and dug it out. It has kind of a “butterfly” shape. I modified the post to fit the Contender. I’ve been using it for three weeks full time and it works great - very little rotation. It is thicker in diameter than the original. I don’t notice the extra weight and actually think it might be more comfortable. The grade of stainless steel is not as good, but is doing fine. Im thinking about asking Mark to make one. This is a similar ring from eBay - the R4:
I love the ergonomic A rings on the chinese cages numbered in the A270s eg the A273. They dont rotate and because of their diameter they grip and dont slide. I'd kill for a small Contender or Jailbird with that ergo back ring.
I had Mark from MCN fabricate and install the pin. I ground down and shaped the ring myself. I've also done some plastic versions using CB 3000 rings.