Tim,
Hans W, designer of CDC and Elk uses Coastal Deer Hair for the wing instead of Elk - not sure why he called it a CDC and Elk ! I quite like Elk and recently got some great patches from Toby at Funky Flytying ( Early Season Cow Elk) that is perfect for this fly.
When I was in Orvis Banchory yesterday they had some really nice Elk hair, including a bleached patch, as well as good 'bulk' boxes of CDC ( I use the Orvis stuff).
Hope this helps,
Lindsay
PS I tie a few CDC Elks with less hair but with an underwing of light Orange poly-yarn, Cinnamon Aerowing. I feel it gives the wing a bit more 'structure' and silloutte.