ideas to drop resonant freq?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Laurence Davis by way of Terry Fritz <twftesla-at-qwest-dot-net>" <meknar-at-hotmail-dot-com>

I've tried various things to drop the resonance on my coil. its tapped at 
between the 4th and 5th turn. its using a about 2500w with 4 12kv/30ma NSTs. 
I've learned a few things in the process, but haven't dropped the freq yet.

heres a list of what I've tried. I'm looking for suggestions on what to try 
or what to test.

1) tried wrapping a new secondary. but miscalculated, and have fewer turns 
than first secondary (which will raise resonance, right?).

2) removed 300ft spool of RG6/u that was being used to connect to my ground 
rods.  essentially an air core inductor.

3) removed 1 or 2 NSTs to better match resonant cap needed. here's my logic 
on that.  java tesla calc says resonant cap for 12kv/120ma is 26nf or so. 
which my cap is within 5pct or so.  supposing that cap value needed is more 
than what i have, then reducing number of NSTs will reduce the cap reqd. 
therefore will lower resonance. it didn't.

4) learned that there are "diminishing returns" from increasing the spark 
gap distance. Also interrelated was the top load required changes per the 
spark gap dist.  meaning: the spark length maximum is not at a wide open 
spark gap. (does this sound accurate?) this I would guess affects charging 
time of the cap.  in essence, there is an "optimum" spark gap maximum 
distance with regard to spark output(which could be read as spark length, 
more or less branches, decibel level, etc)

5) next tries will include a smaller dia secondary with less turns, and a 4" 
secondary with more turns. significantly. perhaps 30-50% more.  and a larger 
cap that is adjustable AND in a smaller box.  i'll aim for 40nf with 5nf 
steps, and break the last 5nf into 5x1nf.

experimentation helps me see the truth behind the math.  I wish i had a 
stronger grasp of the fundamentals behind it all.  with time it will come.  
thanks for any comments.

Larry.