Custom spring work in some cases is a shot in the dark anyways......at best an educated guess even with all the factory specs laying right in front of you. On the other hand, I too am a victom of a bad set of springs from Alcan. I ordered 3 sets of springs, all the same, all for W250 Club Cabs and all were different. We installed them at the same time and my buddies rides were close to correct although one had too much rake. Mine, on the other hand, looked like we added 4" blocks to the rear and did a spring under in the front. It was a major ****** moment.
I have history with Alcan. I use to be consumed by IH. I drove scouts and had several 1110 and 1210 4x4s. Try to find a lift kit for a 1210....it aint happenin'. So Alcan built every set I ever had (over 6 sets). I called em up and although they didnt send me a refund for the dodge springs he did offer to rework another set at cost and even ship for free. So I also had to buy two sets.....it was a bummer but oh well. The new set came in and worked perfect.
Now with that said, I own a machine shop and theres no way Id ever stick a customer with a bill if the mistake is on my end........no way. I guess thats the way they roll. That business model seems to be working well for them. Call me a slow learner, or a glutten for punishment but Id call em again. One snafu out of 9 otherwise theyve done excellent work.