Scud off the top of my head I can’t remember the distance to helms and I don’t have my little map with me. But to answer your question about what is the best situation, I would without a doubt put in at the dam after 7 and fish the falling water. 2 or more on the Cumby can be too much current to try to fish and not sink the boat at the same time, especially if you’re without any kind of motor. My favorite time to fish big streamers is during falling water so you’re going to be in good water all day. Toss anything white on the sink tip and experiment with retrieves. When you come to a timber lined bend in the river and you get that fishy feeling put the fly as close to the structure as you can and rip it back to the boat. One thing I have found is bends or areas behind islands where there is a gravel bar close by seem to be the best areas for me. Deep featureless bends I usually just motor past.
White 1/100oz fly fishing marabou jigs might work well for the Boo guy if he isn’t above using them. Otherwise some kind of minnow pattern cast out and drifted along with the boat and close to the bottom. You could also put in at Burkesville and float to Traces on the Cumberland with falling water from tonight. This section is known for producing some good Trout but I don’t fish it much.
Me,,,, I am still at work 16 hrs later. Man, this working for a livin sucks.
Good luck