Leave loose pop or beer near the top of the packs to move for ballast, or as stated earlier, use rocks. Never bothered using the scales, get the weight close , get it on the mule, and get down the trail. The weight alone may not be the balancing factor to begin with. If you have to packs weighing the same but one has the majority of the weight higher than the other you can still have the load roll on a pack animal.