I would ditch the add a leaf, I can almost guarantee that that one leaf is stiffer than the whole pack (if it is a lift aftermarket add a leaf).
The overload spring might slightly limit how far the springs compress. You might want to ditch that too, but if you do make sure you use a bump stop or something to keep the pack from arching too far negative (so you dont bend the springs or damage them).
My
Hope that helps
