Stan, I'm in the same boat you are. A little bit of negative arch is normal, but the ride should determine whether or not you need the springs or not.
In my case, my right front spring is weak, I can feel it when I drive and I can see the abnormal wear on that 1 tire. Good shocks [and tires] will help, but they will only mask the bad spring until they wear out.
If you have any cupping on your tires, then that is the tell-tale sign that your springs are not doing there job.
What happens, a normal working spring will create enough downforce to engage the suspension, kind of like forcing the tire to the ground. Without that force, the tire tends to bounce or "dribble" like a basketball, that creates the cupping wear on the tire.
You can cheat and throw a helper spring on there for the time being, but that is just a band-aid, same as with air-bags.
With that extra weight of your 1031 box, I would definitely invest in good springs. Like the guys mentioned, Off-road Design or BDS seem to make good quality ones.
BTW, you may have already answered this, when is your show going to air?