Check out posts #47 and #49 of mine in Pok’s Manafont thread here: Many Interesting Flashlights from MF (07/10/12)
Basically, the OEM driver was very inefficient and even with sense resistor mods, couldn’t provide more than a max of 1.3A to the LED (stock 1.1A on two cells).
The pill has a solid flat surface and there’s already thermal grease between it and the star, but the driver cavity is very shallow. None of my go-to two cell drivers would fit. In post #49 I describe a new 2+ cell driver that I got very lucky with, and was able to fit it and drive the LED to 2.7A on high with little effort and know-how.
I love the light and hate the (stock) driver.