Actually, I'm planning on using an AR-7, with a shotgun shell holder with a flap on it to carry a SAK and some tubes of supplies. I'll be using a sling that will be laced on the barrel when needed, rather like the leather handgaurd on the supressed Sten from WWII, which will have a couple of small pouches attached to it.

The joy of this is that it can be very easily adapted to any rifle or shotgun.