RE: Best "SIMPLE" rifle sling
I got the Ultra-Flexslingat a gun show. It is a bit $$$, but awesome for anchoring the gun on your shoulder.
I had a nylon and it was horrible. Now I can climb or walk without constantly adjusting or worrying about my rifle sliding off.
Haven't needed to wear it backback style (crossing the chest), but it should be good forlonger treks.