We fished the Williamson last summer and it is a hard river to fish. The best advice I could you is to keep your flies relatively small and then go with a flourocarbon tippet. We fished nymphs with intermiediate sinks and had fair luck. The fish are regularly pounded so they are tough to hook-up. Don't overlook the froggy water, this is where we found the big, lazy lake trout to be hanging out. Check with the fly shop to find the flies to use - I can't remember. Good luck