Research and development by racers and race valve spring companies
I've been told by several different cam companies to shoot for between .060 to .080 from coil bind on any solid roller valve springs, I've used those suggestions for years now
Some things that we justify in our minds, especially on race parts, don't make it true
Spurgoen Goins years ago, who owned AFR at that time , told me to compress every valve spring within .100 of coil bind in a vice and let it sit for at least 4 hrs. to allow the spring to "normalized" He was doing contract work for GM and Jr. Johnsons NASCAR team on the valve train and cylinder heads at that time