Help with high voltage cap bank for Tesla coil

I recently bought seven 1 foot by 8 inch glass frames at dollar tree. I have view several videos on how to make glass plate capacitors, but was wondering how size effects the voltage level or how the number of plates play a role. Tesla map recommends 9nf capacitance, but why is this important would it be ok if it went over? Also if anyone has ideas on the construction of the cap that would be appreciate.

the thickness and composition affect the breakdown voltage, the composition affects the dielectric constant.... the reason for a specified amount of capacitance is because a tesla coil is a resonant circuit, and if you are building yours according to a set of instructions, you need to insure that the primary and secondary circuits are resonant at the same frequency for maximum energy transfer.