I have found one thing out over the years about Flathead in spillways and below dams. I saw a post talking about it a while back and here is what I have learned. If the spillway has current breakers the flats will hold right up against those concrete breakers even if the water seems so fast that it is unfishable. I fish a couple of spillways alot in kansas in may and june when they are releasing alot of water. If you can get away with using 12-20 oz of lead and get your bait to sit in that strong current right below those breakers, you will have a good chance of hooking into one. Most spillways have concrete blocks that break the current near the bottom so the fast water doesn't scour out the bottom downstream. I caught a 62 pounder last may at Pomona doing that. it took me several casts to get the rig to catch bottom and hold the first time I tried it and within 20 minutes, I caught a 62. I have caught quite a few between 15 and 40 since then too. Not to mention one that took me all the way down the river and broke me off. The only reason I ever figured it out was when I saw snaggers get up on top of the spillway walls and waylay Flathead illegally right in the strong current.