The one I am thinking about getting a sling for is a Colt le6920 magpul, so I guess I could run it through the slot on the side. I also have an Armalite A2 I was also wanting to get a sling for but it is a bone stock everything on it. All I would have on that one would be the standard mounting points. Kind of limited on options there but for some reason I kind of like the look being unmolested and all. The colt will end up being my money pit when its all said and done!
I'd probably get a QD attachment point to mount on the MOE handguard or a Colt side swivel mount for the FSB for the front, attach it to the stock and call it a day. You can set it up a lot of different ways with aftermarket end plates, etc. if you don't mind spending the extra coin.