The purple spring is right. The secondaries fully open with no hesitation. I can really feel them come in between 3500 and 4000rpm.
I have attached pictures to show how I could confirm the secondaries fully open. There is a black zip tie around the secondary butter fly shaft. The first two pictures show it before it is driven and the last shows the zip tie slipped on the shaft to show they fully opened.
With the black spring the shaft turned about 5 degrees.
John
