I have had a great deal of success with the flash-backs and flashy nymphs in a multitude of patterns in the Eastern Tn streams and tail waters. To a greater extent, I have more success when drifting one through some of the quicker runs. My take on that is when the fish has little time to examine the nymph, the flash catches their eyes and provokes them to strike. I think you will find them productive as I have.
God gave fishermen expectantcy so they would never tire of throwing out a line.