I would use one of 2 patterns. Either a Chuck's emerger... or a JoeBob's emeger.
Known as 'The Old Man of the Norfork River', Chuck Davidsons pattern is legendary... and the JoeBob is just a variation. 2 of the deadliest patterns on the Norfork for over 25 years. Size 18.
Blue Ribbon Flies sells both.
( I took a 12lb rainbow on the White in the RV park on a JoeBob's fished with a tiny shot )