I am going to leave the brown and put the purple spring back in. This is how the distributor was setup out of the box. I never ran it this way, I pulled the purple spring from the get go. This will give the stock "two step" advance curve that is described here: http://www.loco4fomoco.com/MalloryAdvanceCurveKit.pdf

The summit curve kit I linked to above was probably an unnecessary expense, but it was pretty cheap (20 bucks), and the keys are handy. We'll see how accurate they are.

I took some measurements and organized the data. That purple spring is really stiff! The above document says that all advance should be in by 3500 RPM. We'll see I guess. Hopefully this info is useful for someone.