>>8769600well the KSG has the 2 tubes next to eachother, so it would put the box to the left or right (perhaps even exchangeable for lefties when you strip it)
I think that would be the easiest way to do it, if nothing else. Actually by making the mags interchangeable, you could have 2 tubes, 2 boxes, or 1 of each. Would make it pretty bulky though (imagine a left and right drum mag). it's even possible to make it feed from both mags, like the UTAS UTS-15.
the possibilities are limitless, but at the end of the day, will you even be able to lift the motherfucker?