Moving the leaf springs inboard reduces the wheel rate about 10# per inch, so similar to running a lighter spring rate in the stock position.
Now, whether or not the butt dyno can feel a 30# rate change per side is highly subjective.
Only in roll, to be clear?
This would be in both ride and roll rate because the mounting location is altered, impacting the geometric formula.
You are a member over many years I seldom ever disagree with, but this is one.
Leaf spring location with a solid axle relative to the tire contact patch does not change spring rate in ride, as there is no motion ratio other the 1:1.
