Well, after several more attempts at devices (read as: money thrown away) I am on the verge of giving up with what is available at my disposal. The base ring size is giving me the most trouble. 50mm is too large. 45mm is too small. At the recommendation of a reader I purchased some of the moldable plastic that you can heat in water in order to make the 50mm ring a little bit smaller. with my first 2 attempts I used too much plastic, which caused a new pinch/rub point. My third attempt I used less plastic and the result was an excruciatingly painful nut crush as it slowly slid through the gap. I may give it another go in the future but right now it feels like I just can't win.
I have debated trying Plastidip... but I have read mixed things about its safety with long-term skin contact so I'm a bit wary. The last thing I would want is cancer of the junk caused by a chastity device.
After all of this I ended up going back to the CB-6000... which I already owned, before I set upon this year's repeated failures. It isn't comfortable, but it doesn't allow slip through nor does it have any rub points that will damage the skin. It's a bit frustrating though. Maybe 2018.