I don't think our springs have a progressive rate either but even if you cut each spring exactly the same as the next they will turn out a bit different. And I knew beforehand to keep them as cool as possible while cutting them. However my car sits 1/4 inch lower on one side in the rear and I removed the exact amount from each spring. (I have the pieces) Not to mention that the way springs are made they loose some tension when cut. At least that's what I read. If I had a spring tension device I would not be surprised to find a difference from spring to spring after cutting. But on the other hand, I have the lower center of gravity that I was looking for, the car handles much better with the cut springs than with the Eibach's and except for the rear being a touch bouncy, I'm thrilled with the results. I want coilovers in the future to be able to corner balance the car by raising or lowering each corner. Spring experts cringe if you mention cutting a spring. It's most likely for a good reason.

Les