I think the SMB population improves the farther down river you go. Jim Thorpe has SMBs but only a fair population and the fish are typically on the small side with the occasional decent fish mixed in. At least that is what I've experienced.
I ran into a large school of smallies just below Leslie Run, some decent sized ones as well as the smaller ones. This was around a large back eddy. It might have more to do with the type of water than the location. Also caught the small ones up around White Haven but not with any consistency or size.