Original poster: "Garry Freemyer by way of Terry Fritz <twftesla-at-qwest-dot-net>" <garry-at-ndfc-dot-com> I use a simple technique for two contact gaps ... Connect your high voltage source to the gap you intend to use without attaching the capacitor. Gradually increase the gap until you reach the maximum distance where the gap can easily be jumped by the NST and that is the gap spacing I use.