By the way (this is something I realized as I was reading over my treatise a few postings above), frailing produces a more driving rhythm than does up-picking because in up-picking, the energy behind the picking motion is produced largely by the muscles of the finger(s) and thumb, but the picking energy of frailing is produced by the arm and shoulder, with chest and back muscles, even stomach and leg muscles, involved--it's much more of a whole body effort. There's much the same difference between finger picking and flat picking the guitar. I'm not suggesting that good guitar (and banjo) finger pickers don't swing: Merle Travis and Earl Scruggs sure do. But it seems to me that frailing and flatpicking are a form of dancing: when the whole body is bouncing, rhythm comes easy.
One other thing I noticed about my discourse: I said about doublethumbing that it was finger up, thumb up, and in a sense it is (both are up in that they are away from the banjo head), but the finger and thumb are of course working in opposite directions, so finger up, thumb down, finger up, thumb down.

--seed