I'm a 4 leaf man Dave, i've also lub'd the leaves with ACF 50, spraying it in with weight off the spring to maximise penetration (and also with weight on the spring).
I have a set of Peter Mulberry's anti wind up, high torque jobs laid on the shelf ready install if i can be bothered, just don't feel it'll give the compliance I'm hoping to achieve.
I did change the rear shocks for Bilstiens to match the front which has the SSL system and i imagined a slight improvement. I've tried it with and without the Panhard rod but detected no change.
Yes, you are right of course, a few miles in a converted car over various terrain is the only way.