I can't say as that I've ever had trouble with a thumbpick -- especially trouble with it staying on. If anything, they seem really tight. I lick my thumb before I put it on and it never moves (I do the same with fingerpicks).

I do find it interesting that those who have success upstroking with a thumbpick are doing so with the Kelly slickpick -- a pick that is smaller and has less resiliance (isn't as tight). One might suppose the Kelly more likely to twist or fall off on an upstroke (as opposed to the huge but tight National)

If I have "trouble" with it, it's as I observed above -- I can't upstroke easily with one unless I 1)change the angle I place it on my thumb, and 2)still hold the "pick part" between the thumb and index finger. And, rather than go through that, I find I just play easier and with better tone if I just use a flatpick.

The difference I'm talking about in my first two posts is, again, that a pick that is made to wear on the index finger but act as a flatpick MAY solve some very big problems for 1) stressful performance situations, or 2) physical problems that preclude the ability to hold a flatpick well.

I would never argue (at least I don't think I would argue -- I haven't developed a prototype yet) that a flatpick wouldn't be superior and more versatile, just that there may be an interesting alternative --AND-- I think it's fascinting to discover that when a pick is worn on the index finger all the dynamics change.

Are your hands relatively small, Don?