Ok, here's the deal:

The following is the most effective way I know to
fish small, unweighted nymphs in medium to deep water.
This isn't necessarily a tailwater strategy, and it's definately
not a spring creek deal. It is, for instance, the way I like
to nymph-fish rivers like Montana's Gallatin, Yellowstone and
Madison above Ennis.

Strike indicators have made a big splash recently. I use them
a lot myself. Except my strike indicator
is always a fly of some sort--so I can catch fish on the
bobber too; sometimes it's a bushy #15 PMD in front of
an emerger, and sometimes a big foam-bodied fly on top
of a fat stonefly nymph.

But indicator fishing doesn't work so well for bottom
hugging riffle fish, and even less well for nymphing
into deep, rolling runs.

In freestone streams and rivers--especially for rivers
like Montana's Yellowstone--the most reliably effective
way to fish nymphs is to fish an unweighted, free drifting
nymph in deep water.

One way to do that is with a short leader and sink tip
line. But that strategy doesn't work well for small
nymphs because it is too hard to vibe out subtle
strikes. Short leader sink tip rigs are
better suited to unweighted streamer fishing.

Another way (to fish unweighted nymphs in deep water)
is to put weight on an extra-long leader, and to fish without
any indicator. When fish aren't up near the surface, sipping
emergers or gulping dry flies, it doesn't mean you can't
catch fish. It means you have to fish deep with an unweighted fly.

All of the very best nymph fishermen I've ever encountered
fish that way, usually with a surprising amount of split shot
on the leader, 18" to 30" up from the actual nymph.

So here's my twist. I've actually posted this once before.
But as time drifts by, I've become more convinced
this is the very best way to fish small nymphs:

....Use an extra heavy barbell-eyed Crazy Charly as the weight,
rather than split shot. There're two reasons for this:

1) The Crazy Charlie does the same job:
it gets the unweighted nymph down into deep water, but it
also catches fish. It never catches as many fish as the small
nymph, but it almost always catches bigger fish. Often
(usually, in fact) the biggest fish of the day.

2) The crazy charlie is flashy. Because of its pearly-white
crystal flash wing, it catches the fish's attention--
much like a miniature trolling-rig cow bell. The fish do a double
take when the see the Crazy Charlie drift by. And then
they take the nymph.

I'm into my third season fishing this way now, and my
success rate (especially for bigger fish) has never
been so high. I figured this technique out by accident,
several years ago, when fishing the North Platte in Wyoming,
near Gray Reef dam. So, the obvious name for the rig
is the "Gray Reefer." The name is joke, sort of, but
the technique is deadly serious. The Gray Reefer is dynamite.
Works like magic.