The easiest 2-stage mod for an L4 is to shunt the switch with a resistor. The clicky will then select the level, and on-off will be accomplished by twisting the tail.
A 2-stage clicky is possible, but a difficult mod.
You can also use a McE2S from the Shoppe for a 2-stage twisty.
The McE2S module (from McGizmo) is a 2-stage twisty that has momentary access to both levels. The module can be housed in various tailcaps, ideally in the Aleph tailcaps.
You can determine the brightness of the low-mode by chosing the resistor of the McE2S. The low-mode is unregulated and wastes power in the resistor, you must know that.
If you wanna know more ... you can visit the McGizmo forum, click the FAQ-sticky and read the Aleph FAQ. There's everything Aleph and McE2S.
Some pics:
Aleph Tailcap iterations (E-Series compatible)
SF L4 with Standard Aleph Tailcap and McE2S
McE2S module diagram
bernie
P.S.: the Z57 resistor mod is nice, too, but has a different user interface. It is all a matter of choices, and with the SF E-Series we have a lot of them ... life is good for a flashaholic with E-Series
Wow, I didn't know there were so many McE2S switches! I guess I lucked out, because the one I managed to get looks like it's be my favorite, even if I had a choice. I got the FT.