Any reason it HAS to be attached to the pack? Have you tried a 2 point sling let out long enough to carry over the shoulder so it carries across you about waist high?
No, put it around your [bleep] neck.
Why would you want to put it around your neck and focus the weight on a smaller area instead of spread the load out and where the rifle is more controlled?
"My message to my troops is if you see anybody carrying a gun on the streets of Milwaukee, we'll put them on the ground, take the gun away and then decide whether you have a right to carry it." - Milwaukee Police Chief Ed Flynn