normally the letter 'a' (anular) is used for the ringfinger. So ami for the three fingers. Just to avoid confusion, if any.
I remember that from classical guitar study, and considered using it. But since I want to reach beginning and intermediate players, and since it's a pretty logical substitution to remember, I've gone with the "r" in recent years, and the people I work with seem to find it easier to remember. If I catch any grief for it, I can always use the old "your honor, I'm from Kentucky" defense.
NHOP right hand is really great. But I think it is personal/specialized technique that is not for everyone.
Also you need you use your ring finger regularly because if you use it only once and a while you will get blisters very fast.
I completely agree, and I use it very rarely in performing situations. On the other hand, bass technique is an evolving art form, and it fits the concept that applies to the two finger patterns. After going back and forth on whether to include it, I ended up feeling that it would be best to present the four patterns involving the index and middle fingers as the regular deck of cards that most games are played with, and throw in the NHØP pattern at the end as the joker in the deck, stressing that most card games do not require it.
The whole NHØP three finger "banjo roll" technique question is a big one for me at the moment for the reason that you mention - the same one he mentions in an old interview in Bass Player magazine from years ago: it's something that you either have to do as a regular part of your playing, or not do at all. It has several built-in complications from technical (the ring finger is the least coordinated/independent finger and gets the least amount of surface on the string of the three we can use) to practical (gotta keep that callus strong, or the game is off) to musical (playing articulation groups of two and four with an uneven number of fingers creates a lot of permutations that can be confusing).
It is the very last of these - the "permutations" - that makes me feel that it should be included in a primer on right hand technique, since the whole premise of my right hand philosophy is that as improvisers, we have to practice all technical possibilities regularly to the point that they become instinctual because most of our mental energy will be used conceiving the musical lines themselves, and the technique has to be automatic; start thinking about fingerings, and your lines will suffer. But if you regularly and systematically practice all of the various fingering permutations your are likely to use while improvising, they should eventually become a subconscious flow that doesn't detract from your conscious attention. I have dabbled with the three finger technique, but I know that the reason I haven't used it more is that I haven't practiced it enough. I firmly believe that if I do, it will become a staple for certain musical situations where it has advantages over one or two finger technique. All of this is to say that while most people will probably decide not to use it, and while beginners should probably focus on the simpler techniques first, there is another option for advanced players should they choose to pursue it, and I suspect that it could open a lot of musical doors for anyone who really worked on it.
Sorry for the novella - obviously, the coffee is working...