Actually, Dave (or anyone), I do have a couple more question:

Do you worry that too much weight can somehow mess with the drift of
your nymph?

OK, obviously there's some amount of weight that is too much. But I'm
just wondering if I should always try to err on the side of extra
weight. As it is, I can't think of a time that I"ve ever put on more
than two 4's, or maybe one BB - and perhaps that's my problem. And
yes, I'm sure in general I don't do enough to tick bottom. But does
the upside of being down deep always trump the downside of possibly
having too much weight? (Sorry - that sentence came out as is, and
it's just too bad to change it.)

If it makes a difference - most of the situations when I'm
under-confident in my nymphing occur when I'm casting a ways, say about
20'. If I'm high-sticking, then I'm generally pretty confident. (And
part of what started all of this is that I noticed that I have a
markedly better success rate nymphing when I'm close enough and the
water is clear enough that I can actually see the take subsurface - a
much much higher success ratio - made me think I was doing something
wrong in other situations, just looking at my indicator.)