I’m really surprised no one has spoken up about this. I’ve never used DSE’s leaf spring/shackle setup, but I don’t think you’re going to find any leaf spring setup that is going to locate the axle as well as a panhard or watts link...a leaf spring is ALWAYS going to deflect.
Check these guys out
http://fays2.net
They have an adjustable watts link setup you can add on with your leaf springs, and should you decide to change to a different suspension layout later like a 4-link, 3-link, or torque arm, you can still use this watts link.