You sound like a kindred kind of hunter, Frank.
Since you're making your own, the key for me is in a secure attachement at the butt. A simple pass-through loop that sinches up on the stock right below the trigger guard is good. But look close at the butt end on the one I linked. That works well too, while giving you a little more length between the attachment points on the mounted sling. That has allowed me to pass my head and one arm through the sling for carry "across" my back rather than on the shoulder. That's a great boon when the country gets really rough, especially for scrabbling uphill.