I gotta admit I have trouble understanding your end game.
QD sling mount in polymer? Buy the cups, drill the stock, epoxy cup into drilled hole. Worked a treat on the poly stock I wrapped 'round my little papoose.
I’ll try to get you a picture when I get home.
Also, you are welcome to my 1095ts stock if something goes wrong. I won’t be using it 'cause the springs just make my head spin.
Edited to add:
This is similar to the cup I used. Forend on papoose has a keymod cup to receive the other side of the sling.