I have a 4D Mag with 1D extension, loaded with 6xIMR26500 to power an Osram 64440IRC bulb. The switch is modified with a Kiu socket kit and a JimmyM JM-PHD-D1 regulator set to Vbulb=19.5V. The light is topped with an FM Throwmaster head, which works very well with the 64440IRC's axial filament.
very cool, only problem is aw doesnt produce 26500 imr anymore.. or so it appears
i was looking at some possible lifepo4 configurations, but i dont think i can fit the amount of cells in a 4 d that i need. I could try and fit 6 18650s and 2 dummy cells with some kind of homebrew series adaptor (my 4d is quad bored) but i think thats even less practical than 16 aa's
ill keep looking... i only have 4 cycles on my 16 aa's so i have time