For the big ol' salmon flies I find it is hard to beat the good ol' Sofa Pillow!
Make sure you only use just enough hair in the wing to give the silouete of fluttering wings. Many people and pro's make the false assumtion that the sofa pillows wing helps in floating the fly and tie in WAY too much hair.
Example:
This extra weight ends up actually making the fly float worse and cast crappy. Idealy you want all of the wing out of the water and the fly to float as high as possible so that you can skitter it. Also its important to use the stiffest, highest quality hackles and lots of it (very hard to find high quality hackles for a size 4-6 fly).
Here's a pic of a good looking one (though the hackles look a little webby):
Finally use nothing less than 4X (where I use to guide we would run straight 3ft 12lb leaders). If you use a tippet that is too light the fly will spin, tangling your leader. You will also have a harder time turning it over and you will lose more flys. If you can get away with it use the heavy stuff!
Later in the hatch I will switch to the rogue foam stones to match the spent bugs.
Man do I miss the Gunnison in June/July!!!
(drool....)
Nice looking flies!

GRIFF
PS.. I am in for a swap!!