question about weak arc

Hi everyone:  am enjoying reading the contributions of those farther along
the Tesla path than I am so far.  My coil is about 700kva with 2 paralleled
neon xfmrs 12 kv at 30 ma each.  The cap is made of 1/4 in. plate glass and
is about 0.016 mfd.  The coil does a nice corona discharge with 8 to 10 inch
arcs.  The s.g. is a simple series gap, adjustable.  

My question is should I go back to the drawing board on the capacitor?  I've
been reading about the polyethylene sheet caps submerged in mineral oil.  My
first attempts at capacitor manufacture used simple window glass, and I
found the glass was punctured quickly.  Thus, the 1/4 plate.

I believe I've tuned the coil to its optimum arc output, and that I need to
experiment with a different type of cap?  

Feedback would be welcomed!!    Revel in the corona,  Steve.