So, I’ve finally got an A-ring and spacers (well, the spacers between the A-ring and the cage consist solely of the inverted arc of the largest A-ring from the CB-2000) that work.
This setup, with the middle length post and the approprate spacer, makes the solid spacer hold even the plastic locks hold things nice and tightly.
After a few tries (the plastic locks kept breaking) my current plastic lock is #150702. The KH says it’s on until Monday, when we roll the dice. Obviously we’re now playing by different rules than before, and I’m not entirely certain what they are.
I did get a few minutes of teasing after the first lock was put in place, which was fairly exciting. It was also a prelude to me deep-throating the KH for a few moments after fetching things for him, which is making going to sleep a little difficult…