Thanks for reminding me of the year he died Salmo_g. It was the 1970's when he moved to Seattle to be closer to his daughter after he retired.
I know after he moved to Seattle, Walt's flies made a major transformation which I attribute to Syd's influence on him and his tying. I also know it was about the time Syd moved to Seattle that Harry's flies also changed, but since Harry also got to know Pat Crane, it may have been the influence of both that caused the change in Harry's flies.
I also know that after Trey had his second book published by Amato, the nature of the steelhead flies the larger perverers of steelhead flies changed their character to a more streamlined fly from the over-dressed, chenille bodied, heavily winged ones they had been selling.
Syd's influence is seen in many ways large and small amongst steelhead and Atlantic Salmon tyers and fishermen. Hair wing flies became sleeker and sparser, feather wing flies came back into style and use, spey and dee flies began to be used again, and I dare say he was responsible for the resurgence in Classic Atlantic Salmon Flies we've witnessed here in the PNW. In fact, the NW Atlantic Salmon Fly Guild I see as the direct result of Syd's influence.
He never put a material on a hook that didn't have a purpose, and that includes his Classic Atlantic Salmon Flies. Alec Jackson once told me that Syd said that good fly tyers don't have to overwhelm with amount of material or shear size of fly, but rather like well-trained musicians, they used subtlety and skill instead of the bad rock musicians who simply played loader to cover their lack of skill. In my own tying, I strive to make sure every material has a purpose and that the result has the sleek, streamlined, fishy look to it (that's what Bob Arnold refers to as the best fishing flies for steelhead).