the problem might the arc of the panhard rod.
a panhard rod will move the diff housing sideways as it travels up & down.this could be why you're getting tyre rub.the only way to minimise the movement is to get the panhard rod in the middle of it's arc when the car is at it's normal ride height.then the diff will only move a small amount,either up or down.a watts linkage,which is a z or s shape,depending on how it's fitted,doesn't do this,but is much more complicated & expensive to make.