I've been reading this thread and have not really seen this point discussed and I'm curious what you have to say about it.
Take a rear axel completely removed from the truck so there is no weight placed on the springs.
Place one wheel on a brick, tie a piece of string, with a weight gauge to the wheel on the other side and lift it so the axel is horizontal. Measure the weight on the gauge, I have no idea what it is but lets say 200lbs.
Now put the axel back in the truck but only connect one leaf spring. Put a brick under the wheel on the side with the leaf spring connected. Now lift the side without the leaf spring with the string and gauge. The weight measured will be more than the 200lbs measured in the first case because we now have a second class lever.

So the downward force on a drooping tire on the ground is made up of the following
Gravity
Shocks
Force from spring (+body weight) on the drooping side, this will become negative at some point
Force from spring (+body weight) on the stuffed side, this will eventually come to 0 (tire to ground) when you hit the bump stop.

Now if we get to full extension and unbolt the axel from the spring pearch and measure the force between the axel and body and between spring pearch and body, what would we measure? And what does it mean?

Richard