Air Bags/Springs - Firestone, Air Lift or?

I do not know it to be true, but it looks to me the lower Stable Loads takes away the progressive action on the lower overload spring. Without the lower Stable Load, the lower overload makes more more contact with the spring pack as the load on the truck is increased.

I have no problem with the upper Stable Load, It simply allows less drop before the upper overload engages.