So, I am currently running a Mallory Unilite Optical dizzy, 2 grey springs, 12 degrees initial, 28 degrees max. NO vacuum advance.
The chart shows the effect of the various spring, this is in addition to the initial advance..

This gives me this:

Or as a table:

As you can see I have done a slight 'kickup' below idle rpm, read that this is a good idea as it helps improve idle stability.
Can someone check my thinking through please, and please tell me if I am doing anything silly!