A conventional box requires a pan hard or track bar other wise the body and frame will move independently when steering. A pan hard with double triangulated is likely to result in ripping off the bracket or nasty bump steer.
The double triangulated 4 link keeps the axle centered thru out the suspension travel where the pan hard will pull or push the axle side to side. Running both causes the pan hard to rotate the axle during articulation. It will cause one side of the axle to drop and the other side to rise. This in turn will turn your steering wheel due to the drag link.