Misunderstand? Me? Never! (laughing)
Sorry about that, Rich, and thanks for the reminder about the perils of assumption.
Do you mean your plucking hand is sort of in the Stanley position, but with your thumb and hand perpendicular to the face of the bass rather than the parallel position Mr. Clarke assumes?
That's a good question. Maybe a layer or two of medical tape over the tip of your thumb secured by one turn around it? As far as I know the cloth kind is non-reactive, but if you choose this route it'd be a good idea to stick a small piece of tape somewhere unobtrusive, like under a pickup, to test my theory for a few days or weeks.
Good luck!