Tesla power

Greetings again:

I still have not fired my new coil but expect to in the next day or two.
 Once I get it tuned at low power, can I just keep adding more power
(transformers)?  I am running at 12kv and have two 30ma transformers that I
will use for tuning.  I also have two more plus a 120ma transformer  -
 2.8kva total.

A circuit question - I understand it is recommended to use a variac and bring
the power up slowly.  My spark gap doesn't fire until the variac is up to
about 75%.  If everything is linear that would be about 9kv.  Does this sound
right?  Once I get the coil tuned, can I eliminate the variac?  It won't be
able to handle all the transformers anyway.

Thanks,  Ed Sonderman