OK- - - - -this discussion isn't going to change any "hearts and minds" like they used to say about Southeast Asia, but the way we evaluated modifications on the racers was to chain the frame down to the floor on adjustable screw jacks at the desired ride height, assemble the steering and suspension without springs, and cycle it through the full range of travel while actually measuring bump steer. With a leaf spring setup and a straight axle, that would require fabricating a swivel arm to position the axle in place of half a spring, using the rigid spring mount as a pivot point. Nobody who is participating in this discussion is likely to do that, so I just wasted a couple of billion electrons and a few minutes of my time!
Jerry