I use a very inexpensive ebay loop sling with a shock cord included.
I made a loop strap from some nylon strap to loop through
any gun I own. The little clip hole was off a sidexside
safety netting I had lying around. Like I mentioned I put it
over my head and it drops to the side. The gun hangs right where
I can reach it to swing up for a shot. Can't slide off my shoulder.