OK guys... I came up with the ultimate solution for this problem. I thought the answer was going to be a GG&G sling mount - one of these:
However, when the part arrived, I quickly found that it would not work in conjunction with the ATI top folding stock - the stock folding mechanism was in the way.
So, back to square one - what could I use to attach to the sling mount on the ATI top folding stock? I finally settled on one of these:
A grenade pin. It's hardened spring steel, I have no idea how strong the thing is, but OMG it is hard and strong. It took a screwdriver to get the pin apart sufficiently to slip it onto the sling mount on the folding stock. Once on, I just attached the single point sling to the grenade pin. It rotates, it's strong, it's even a dull army surplus green... not quite the "tactical black", but not bad.
The best thing is it was free at the local army surplus shop when I bought some ammo cans. I'll post some pics here in a bit...
Here are a couple pics of the end result: