[Jeff Lee]

Having something (AMX) that doesn't offer an aftermarket front spring, I went through the same thing, having the same requirements as you. I used a place called Coil Spring Specialty and had custom made springs. It was frustrating but in the end, we got it right. I think the 4th or 5th set got it right. The first set they really screwed up. They made them for a front weight equal to the total weight of the car! I knew something was wrong because I couldn't compress them more than a few inches with the spring compressor.
The good part about using a high quality part is the car has never dropped at all in 10+ years. That's something to consider as I know those that need to replace Moroso springs every year or two. And you know it's time to replace them when your car starts launching funny. Do you loose a round or two on the way to figuring out your springs were bad?
Calvert makes a front shock that is a lot looser than the QA1's. He discussed valving with them and they didn't feel they needed to make a shock as loose as Calvert wanted. So he found another source that would make them to his specifications. I have a buddy with a D/SA 402 Nova and replaced his QA1's with Calvers and the car went quicker all around.
On the Santhuff's you've had, has the wire diameter been reduced as you try different sets?