I'll be curious to see how much/if your leaves settle. Unfortunately since adding the add-a-leafs I've lost about 1.5" in the back ([edit]--lost 1.5" from the original height the springs settled to w/ the add-a-leafs in, they still added a good inch in the back.)
I'm not sure if anyone else is having the same settling problems, I know Will has the same setup I do (trashed stock springs, shackles and add-a-leafs), not sure how much his may have sagged.
Maybe I need to call Alcan back and hurry up w/ those springpacks...