All Things SUB-2000!
I have a sling option you may like.
Allows you to carry open or folded, does not interfere with mag change or use of charging handle and can be rotated mid-line to allow the drawing of a sidearm.
Shoulder holster carry: By folding and attaching both ends of the sling to butt stock you can slide rifle under your arm.
I believe the D-Ring base has provided enough surface area to not stress the screw or frame. I used a torch to remove the silver finish from D-Ring and then blued it. The loop on the butt stock was made from parachute cord.