Well, the rear housing moves side to side a couple of inches when the car goes from setting at normal ride height to jacked up. This of course is caused by the rotation of the panhard bar, the single upper bar has enough movement in it to allow this but add another upper control arm and it has to restrict this side to side movement which binds the rear. On the circle track cars we used the truck arms which form a wishbone under the rear, the rear mounts solid to the arms with only the panhard bar to restrict side to side movement. Hell, I don't know, I can't spell eigraneer 
