Blue shadow, I have the slide springs but, they are still in the box in my garage. When I purchased them I spoke with Barry Holtzman. He said the fellow that was testing for him in the mountains in Idaho was gaining 1,000 RPM by just this spring change.
They are available for three different elevations ranges. They are $39 and if they allow me to throw more weight at my primary clutch I'm all for it. Powder Blue