I am interested in upgrading my low power 4" coil. Primary is 11.5 turns of 1/4" copper tubing wound on 1/2" centers. I was wondering if a 15KV 30mA NST might be all I need for the size of this coil, or if it would be worth it to go for a 15KV 60mA NST instead. Is it possible to "overpower" the coil? Ron