Great choice of flys to post!
Forgotten all about this little bugger; when I lived in Healdsburg, CA (house was 5 minutes to the Russian River) a fly very similar to this was one of my 'go to' flys for low clear winter water fishing.
Another one substituted bright red Swdz with a silver underlay. Both darned effective. Loved it when all the gear chuckers were doing just that ... chucking without results .... and I'd sneak a fish right out from under their noses.
Actually, was pretty easy as the lead caused them to fish the bottom and the Russian River fish seemed to prefer to hold above the bottom in the water col.