[Frank Messina]

Rupert,
Don't forget that you can also use an adjustable vacuum advance if you don't already have one that enables you to tailor the amount of vacuum advance exactly to your engine's needs. All you need is a 3/32 allen wrench which I think you have. In this way you can avoid light throttle detonation by backing out vacuum advance while still maintaning a fairly quick mechanical curve all in by 3000 RPMs. For example I have mine dialed back to 7° vacuum plus 15° initial which allows for easy cranking but a very crisp throttle. Total advance at 3000 RPMs is 35° with no vacuum present. HTH
Frank
PS: Oh and yes, use manifold vacuum only, not/never ported for all the reasons listed above.