The original Reactor 3 had a bad switch design, and also a problem with the tail cap resistor. If you send it back to CMG, they will send you the new version.
You can overdrive it by bypassing the tail switch resistor, with aluminum foil, but be careful not to burn out the luxeon. It won't last long if you use NiMh with no resistance.
You might be able to add another resistor in parallel to increase the current flow. Or just replace the original resistor.
If you don't screw it up, you have a life time warranty.