Thanks for the links. 4x XHP50.2 would be sweet. What driver would you recommend? And since I don’t see a way to re-purpose the ballast, how did you mount the LED and drivers? I’m probably biting of more than I can chew, but it looks like this flashlight has the mass to dissipate a lot of heat. I suspect my original battery pack is not healthy either since it was sitting dormant for some time.