I'm not really sold on the idea you wouldn't need a panhard bar by using just the front or rear section of the original springs bolted to the axle. that setup is basically called a "quarter eliptic" suspension. that setup requires either a triangulated upper rod on each side to keep the assembly in place, or a panhard of sorts. [see mopar ron's post on his latest truck project. he is doing a quarter eliptic with a couple of angled rods to locate the axle.]this is also extremely important if you do a "cross steering" setup, as this will impose forces that will try to push the axle sideways when you turn the axle side to side. I feel that even tho you have the axle bolted firmly to the spring, then the front spring half bolted to the front hangers, without the rear spring half bolted to those respective brackets, that assembly would act like a box with only 3 sides: very easy to move around side to side. if the complete main leaf were to be used in conjunction with bags, then a panhard bar would definitely not be needed. just my thoughts. I have studied suspension design and theory for many years before I built the setup that is under my humpback, and I would hesitate to build in a problem that couldn't be fixed without major surgery.