Dear Stewart, Again a sound analysis. And I do keep the little finger on the soundboard. And for fast runs I use the thumb/index as is proper. But perhaps my right hand is unique, my ring finger is quite independant and strong (and is the same length as my middle finger). Where it likes to get into the action is when one has played a chord that goes into a run where the first note of the run is the weak beat. That good ol' ring finger likes to hit the weak note so that the thumb can come up and start the thumb/index alternation on the strong beat. Not that I am in a position to correct any technique, but everyone has a different hand. (When I have to open a stubborn bottle cap it is my ring finger that does the work - what can I say, my hand is weird <g>).
Best, Jon