i just started doing this today (plucking ring and index) and found it very comfortable.
if you've seen some of my previous posts in the amp and bass sub-forums you may know that i'm recovering from a spinal cord injury. two years ago, i broke my neck at the C3/4 vertebrae. i was paralyzed from the neck down instantly, and i've been fighting to recover since.
obviously, i've recovered enough to be playing bass again, but i still have quite a bit of nerve damage that restricts my playing. i found that my right hand picking was feeling awkward and my timing was inconsistent. i've been powering away with a metronome and hoping to just build my skills with drills.
today i noticed that my left hand (which is the most impaired region of my body, currently) had issues with coordinating the index and middle and that i was compensating by using my ring finger for fretting notes that i would have used my middle for, previous to my injury.
at first i thought that this might be a coordination predisposition in humans, along the lines of the test where you try to pat your head while you rub your belly. the right side and the left side often try to follow each other, so i thought i'd try going with that flow while picking. it also triggered a thought to look up the nerve pathways i'd learned about through my recovery, called dermatomes, which tell you what part of the body is controlled by which vertebrae level of the spinal cord.
notice on the chart above that there is a break in fingers, splitting them into groups of the index & middle (controlled by
C7), and ring & pinky (controlled by C8). it has me wondering if, for some people, that creates an effect on coordination of finger movement. think of it as having a dual processor computer, where one processor controls one group and a second processor controls the other. it may be more taxing on the processor to try to run the "alternate picking program instruction" for two fingers through a single processor than to run two paralel "picking program instructions" with each finger being handled by a separate processor.
i just put this here as food for thought. obviously, whatever works for you is what works for you. clearly there hasn't been an overwhelming number of players that use the ring/index technique.