combining neon xformer cores

Hi all,
    I have 2 neons that I unpoted and I noticed the cores are the
same except one just has more laminations. This is because it is a
15Kv 30ma and the other is a 12Kv mA. I think they are both
France's.  I had the idea that I might be able to combine the cores
to make ones that was much thicker. I would have to wind a new
primary and new secondaries for it, but was needing a little help
figureing out the VA I should use. I figured if I assumed 50mA for
each core that puts the 15Kv one at 750va and the 12Kv one at 600va
giving me a transformer with 1350va. This a good estimate, or would
a higher ratting be fine. On the 15Kv I removed shunts and run it at
54mA. I've yet to remove the botls from the 12Kv and fix the
secondary short in the wood they used as a spacer. I don't know what
the cores saturate at but would like to get as close to 2Kva as I
can. I do plan to shunt it internaly. I plan on making the new
windings for 12Kv so that would put me about 112mA.