Thank you for the post. It's weird that national springs which has more leafs (when compared to stock springs) are actually softer. I imagine being softer makes your rear shocks work more.
Anyhow, you mentioned that with a load in your bed, you are on your bump stops all the time. I have heard similar reports. Some have even said go with HDs to avoid being on your bumps when your bed is loaded. But with an empty bed, HDs spring ride pretty stiff. And hence the dilemma.
they only feel softer because there are more leafs to "progressively" increase the stiffness. since the stock springs have 3 leafs, it's all or nothing, like soft, medium, hard which makes most bumps feel more harsh. with the multi-leaf packs like National and Deaver you can experience a less harsh (described as softer) ride over the smaller stuff with a smoother transition over the larger stuff.