Have you rolled the car on them yet? Did you tighten the eye bolts with the rear hanging down or all the cars weight on the rear? You might try loosening the 3 eye bolts and letting it settle.
I've just been out to garage and lifted frame of car allowing rear end to hang. I then loosened all the fasteners and let droop. I then snugged fasteners then lifted axle with jack and got same result. I think springs are bad.
