There are a couple of patterns that have been very successful through the years on the Holston River. In the early part of the season the Net Builder Caddis Larva has been very good and as the season progresses the Green Caddis Larva , used as a dropper underneath a CDC and Elk or just a plain Elk Hair Caddis have performed very well. You need to be very aware of how the fish are feeding to be successful using the larva stage. There are just some years that they don't key on larva or emergers and other years that they do. Watch the form of the rise to see if it is a dimple or a splashy rise. If you see sides flashing on the bottom, that is an indication that they are nymphing and the Czech Nymph or the Net Builder Caddis Larva is what you want on there. That BHPTN works awfully well too. I'm not going to link the flies, but you can click on Tailwater Trout Flies and see both those patterns. Good luck.