with a 4khz inverter the 9v does pretty good. using one of the 8aa or 8aaa holders that wel sell will make it run brighter. Either will fit a 1.5" sink tube. The trick to making the 8aa battery holder fit is you cut off the tabs that stick up to hold the batteries in place and then it fits and works great. If you have a skinnier hilt or are making a short hilt then I would stick with the 9v.

Tim
The Custom Saber Shop