I have a 2 modded Arc AA's
One is a Madmax R Bin luxeon.
The other is a PIC controlled 8mm led with 14500 cell.
One of the easiest best mods you can do, it direct drive an 8mm led off a 14500 cell in it.
Heres what a 14500 cell will dor direct drive with an 8mm LED.
Not a flat regulated runtime by any means, but, you wont really notice it drop for the first hour or so, and its sill usable after 5 hours.
My Madmax LS one? eh, the MM doesnt to great off 1 AA.
Plus you have to figure out a lens solution, to protect the LS.
The 8mm led you can install just like the 5mm led is.