My buddy from Alaska turned me on to a sling similar to the one below - can't remember the brand I have.
Rifle always at the ready, rifle weight in front offsets pack weight in rear, can't fall off shoulder, carry muzzle up or down
Just an awesome sling for stalking.

http://www.niggeloh.de/index.php/rifle-slings.html - "Rifle Sling 'Driven Hunt'" model