Many good points....thank you.
Trying to think DIR, if there is a problem with a configuration, it should be avoided. The height of the billy ring I have is about 1/2 that of the standard d-ring...therefore, I am not sure it represents any more of an entanglement hazard. A DIR diver is a thinking diver, and before I make a decision one way or another, I want to understand the plusses and minuses. I will likely practice using the side of my thumb until thats solid and then decide I use the d-ring the BP/W manufacturer included or a billy ring. Either way, I will use the same technique (not replacing training with equipment) but I might decide that a rigid ring will less height is actually safer than a floating one with a greater height.
I am concerned that with a stage bottle or two clipped off, there won't be enough d-ring to attach to on the smaller (rigid) one.