adding a leaf spring

I have to say it depends on how it is done. My 1ton Dodge rode like a boat. The suspension was squishy. I took it into a local shop to have them check it out. They recommended re-arching the leaves and adding one. They said it would lift the back about an inch. I was apprehensive but went with it. When I got it back he walked me through what they did. They split the leaf packs out and re-arched the existing ones and added another one to the center of the pack so it is like a factory leaf pack. Not one of those thick overkill add-a-leaf kits. They then put new shocks all the way around. $900 out the door. I am very happy with the work and you can't tell that it is taller.