I have fished the area for the last ten years. Here is what I'll have in my box, green drakes, 8 and 10. Coffin flies same size. Sulfers, size 14; a few march browns, 12; caddis tan, size 14. Some BWO's 18's. Now that all depends on mother nature. Give Dette Flies a ring when you get closer to your time. I usually don't fish the Beaverkill as it is usually crowed most of the time. I fish the East Branch and Willowemoc they are wading rivers while for the best shot on the west branch it's more of a float river. IMO.