Ran across this as I was looking to change out my rear sling attachments. Good stuff. I made a small mod that might interest you guys. One of my M4's was a real PIA to get apart. The pin was short threaded and the retainer plate was force threaded down. I wound up having to red locktite a nut on the other end to get enough grip to break it loose. Anyway I came up with this idea so I wouldn't have to mess with a recessed nut on the opposite end. I put a slot in the end so it can be tightened up with a screwdriver during a reinstall. I was able to get a good tight fit with a screwdriver. If I reassemble with blue locktite the plate (278J) can simply be unscrewed after the locking nut is removed.
My setup. A bit of paper towel to hold the pin for insertion into the stock. The screw slot from above.