Re: Best sling setup for the AICS stock
The TAB GEAR sling, and other slings designed for slung up shooting, is designed so that you set up the front part of the sling for the position you'll most anticipate you'll be in, usually this will be the sitting position which will usually work when you're in the kneeling position too.
I would recommend that you set up the front section of the sling, the loop that your arm goes through, just tight enough that you have to use a bit of pressure to get the rifle into the pocket of your shoulder. With the sling so tightened you should not have to use any help from your firing hand to hold the rifle in position.
After you get the front section of the sling set for your positional shooting you don't touch the front adjustments any more. Now you would use the webbing of the center section of the TAB GEAR sling to adjust for your length of carry. The sling is now adjusted both for your positional shooting and adjusted for when you sling your rifle.
I carry my rifles with the muzzle down and don't have much of a problem with the sling sliding off of my shoulder. I'm not sure how you're carrying your rifle but wouldn't any sling slide off your shoulder if it's hitting your pack? One of the main reasons for the buckles on the TAB GEAR sling is to allow the shooter to quickly release the rifle without having to pull the rifle over his head when the rifle is slung across the chest or back.
If you're a right handed shooter I would recommend you hook your sling to the right side of the stock. That way the sling would lay flat across your hand when you're slung up and not cause as bad a torque in the rifle as it would if it were hooked to the left side.
By Uncle Mike's adapter, are you wanting something to allow a regular sling swivel to be attached to the back of your AICS stock instead of the HK Hook? I don't have any knowledge of something like that.