Of course I couldn't leave it alone. There were obvious candidates for a resistor mod on the driver. The driver is pretty nicely done - thermal pads, thermal epoxy, thick board, sweetest retainer ring I've seen in a while - heavy, large brass.
I could not tell what the limiting resistors are, but there are two large ones in parallel labeled R1. Tried measuring resistance over it, think possible it measured 0.1 ohms, but not sure. So figured I'd try an R100, as shown below:
Well on 2 cells, it sure made a hugh difference!
On 2 protected KP's at ~4.0V, the tail amps on a clamp DMM showed 4.45A, and lumens:
2,050 @start, 1,940 @30 secs
throw: 158 kcd taken at 5m (795 meters)
That's a big bump. In amps it went from 2.55A to 4.45A. It might be a little beyond the peak of the XPL, depending on how much amps is really getting to the LED. 7A to 8A is about peak.
On one cell, it bumped it up but not much. Tial amps went from 3.44A to 3.85A on a LK cell, lumens:
1,350 @start, 1,323 @30 secs
I'm thinking bypassing the springs should help in the single cell configuration, and probably make no difference with 2 cells, where it's well buck regulated.