[Ron Wood]

I received your PM and I am mulling over a reply. There are a bunch of factors involved and I want to think about it a bit. In addition to "pull weight" there may also be some pre-loading that needs to be considered. The pre-loading may already be covered by pull weight and length of the spring but it is going to take someone with a lot more mechanical engineering skills than I have to figure this out. Also as noted, there is significant variance in curvature of the springs even in the small sample I have posted. What is the correct configuration and which ones have already taken a "set" and may or may not be a candidate for a prototyping standard? There may be a requirement for a larger population sampling and I admit that I am loath to start taking the springs out of my collection pieces to increase the sample.
Perhaps these aren't significant factors and the spring company can address them with ease. But it never hurts to have most of the answers figured out up front.