tesla list newbbie

Hi all ,
 I've been monitoring this list for about a year.
 So far I've made 2 Secondary,(4"X24and6X18" with 24 gauge wire) and
assorted primaries
 I use a 9000  -at- 30 nst for power with a static gap of  2  1/4" carriage
bolts with 3pc's of copper (3/4"dia 1/8"between)
ANSI version ----)===(----- , I've used  compressed air quenching  upto 20
lbs usually don't
  For Caps  I've tried  bottles  but never really did that good.
 what I'm using now is  4mil x 2 for each plate per cell x5 cells   in
series (tried 4  but they smoked ) 
Plates (rolled ) were 6X48"  aluminum foil with 8 gage stranded copper used
for connection(strip off 5" ,1/2" folds for 2" then roll )1/2" pvc form 1"
poly overlap
 For dielectric  30wt motor oil was used
  For a torrid I have been using a foam and foil ball.
 Discharges are between 8"-18" 
 dependable , fun to watch 
just cant see what I'm missing  to get longer discharges
  Thank you for all the information this site provides
      David Boggs