I'm not sure but what he probably did is ran the 2 link outside the frame rails. You wouldn't have room with the inner dual on there. I would assume that there isn't room for the 2-link on the inside of the rails with the fuel tank. But I don't know much about them new fangled trucks.
yeah doesnt make sense to put that much stress on the wheel,hubs,axle.. buti think it is possible to run all 6 with a 2 link.. not 100% sure.. but possible..