Stationary Spark Gaps

        I am experimenting with a couple different spark gap designs right
now and would like some opinions from other coilers.  I am working with a
system that operates at 15 kV between 0.4 and 0.9 kVA power levels.  I am
currently using multiple stationary gaps (eight total 3/4 inch copper tubes
3 inches long, spaced 0.02 inches apart, total gap distance = 0.14 inches).

Is there a "preferred" total gap distance which avoids neon transformer
damage and still delivers significant power to the primary?  Am I too close,
too far?

Will additional gaps at closer spacing work better (keeping total gap
distance the same), assuming I provide adequate air flow to quench the sparks?

Mark Rzeszotarski