Ray,

I think one of the attributes that makes the muddler so successful is the buoyancy of the deer hair head. The fly wasn't initially meant to float at all, but you don't want it sinking like a rock either. The sparse deer hair balances out the weight of the other materials, and keeps it moving rather than falling in the current. This allows you to fish it slowly without too many hang ups, thus effectively imitating a bottom dwelling baitfish.

Over the years, I've gone to a denser head than the original, and added a small amount of lead wire to the shank. Same 'balance' concept, but I think the denser head moves water better and keeps the head 'up' more to let the fly move among rocks well.

Buddy