Original poster: Dan Williams <coilerdude@xxxxxxxxx>
I am in the process of buttoning up my 813 VTTC (can be seen at 
www.coilerdude.20m.com).  Tonight I tried a larger unshunted MOT in 
place of the small shunted one I was using.
NO Difference Whatsoever.
Spark length stayed the same, intensity stayed the same.
This dosn't make allot of sense to me.
Someone shed some light?  Maybe suggest what else I might try to 
increase spark length past my current threshold of 12-14"?
Have added a few more taps and tried tuning, max seems to be 12-14" 
at this point.  I know for a fact that this tube is capable of much more.