Need help....

I just picked up 2 Neon sign transformers for $40.00 U.S. Dollars for both.
1 120V 60Hz 15,000V  60ma 900VA, and 1 120V 60Hz 9,000V 60ma 400VA. I am
thinking about just using the 15KV for a Jaccobs ladder and using the 9KV
for a tesla coil. Does anyone out there have any ideas of what type of coil
I can construct with this transformer being used as the input to the
primary? I would like to produce 3 or 4 foot arcs. Is this possible. I don't
want to go any longer than that right now because my experience with Tesla
coils are limited. I want to learn as much as I can before really building a
monster. Any suggestions as what I can use to accomplish this feat? I have
compiled all of the information I can find on the internet regarding
formulas, and have constructed a MathCad file that will automatically
calculate the formulas out for me, but I really don't know what to use to
determine average spark length. Any information/Ideas will be appreciated.