I feel your pain. I got so tired of my rifle trying to swap ends, I put the sling on backwards and carried the gun barrel-down.
Harris is top of the line, with Stony Point close behind, and these days almost as expensive. As to length, the first one I got was a 9" to 13" one, and to me, it's worthless! Too long to use on the bench, and not long enough for sitting or kneeling. The long ones are the best, IMHO.