I have had a plastic grocery bag hanging off the arm rest of my Mitsubishi Delica L400 for years now, driving me nuts.
This hook system works like a charm. I now have the plastic bag hanging off the back of any of the 7 head rests.
Printed in grey PLA to match the seats. No doubt I will have to re-do them after the summer when the interior gets really hot but for now they are working really well.
I used 4 shells and 20% infill. They are strong. No amount of garbage I would want to hang of my back seat is going to break them.