Is it possible they are putting the spring pack together backwards? The bottom leaf looks like it might be much more effective if at least it was reversed.
Haven't compared them to other springs, just a thought.
I am going to replace mine, and I only have 50 miles on them (drove it to Dad's and parked it all winter while I upgraded the front). I expect to have the same issue as racerjoe with a pinion angle being way off. Not sure what direction to go for another spring yet, but have to do something. Frustrating.