Ulsteroid Rear Suspension - Advice Please

[Reckless Rat]

Have you checked to see whether the springs are bottoming out under the weight of the car? You could try noting where the springs etc are sitting in an unladen situation and then where they are if you jack the car up under the rear crossmember and allow the axle to hang down. There should be a goodly difference. It is difficult to see however how much the axle will rise when under load but it may just be that it has bottomed on the underside of the car. Not really ideal...

Some photos might help.