Whenever I see these, they are usually in a relatively tight, large school (compared to anything else up in that area, typically dozens), often milling about near the bottom along slower margins near fast water. They seem to like margins near water-willow. Problem is, they're pretty spooky when you're in the water with them. May be a reason why this is the best photo I have 
Welcome to the forum, Tom. I know Bob (and Joshua Wiegert, if you're a PVAS member) from when I lived in Fredericksburg and have swapped collecting stories and fish IDs with him plenty, though we never managed to get out collecting together.
Thanks for the welcome Derek. Yes, I'm a member of PVAS though haven't really been very active, not unlike my lurking membership to NANFA. I was also a member of PRSC (Potomac River Smallmouth Club) for a lot of years and even a few years in GWAPA. Professionally I'm a beancounter but fish, whether they be at the end of a line, in aquaria or just observing, are my hobby and passion.
Collecting with Bob or anyone who knows what they are doing is a great experience. He turned me on to satinfins and on the same trip we scrounged up a couple of juvenile american eels, astonishing to me as I'd never seen them in small freshwater streams before. I took him out in my canoe (Little Hunting Creek) once - my boat, his brain - and we found 13 species, though not the snakehead fry we sought. Included in the 13 was a beautiful bluespotted sunny, a fish I had never seen as an angler for obvious reasons. (Speaking of snakehead fry, I later found thousands. They are easy to spot in the tidal marshes of Mattawoman and other Potomac creeks, and so numerous. Distinctive yellow color).
Back to spottail/spotfin discussion - your description of their prefered lairs and behavior does NOT sync with my observations of my Cacapon shiner. These do not school tightly, are quite random in their darting about (most likely not randon at all, they are feeding on tiny organisms) and seem to love fast current, have no inclination to hold in SAV.
My rosyside dace are about at the end of their life (over 4 now) while I have all I want 100 yards from my house, I think I may go for a few of the Cacapon minnows next setup.