Fivemega, thank you for weighing in again. I am having a 1xCR123a extension made for the A2. No, I will not be using it with 3xCR123a. My intention was to try using it with 2xAA NiMH cells with a strion adapter and a twin-task 2D bulb. I do not know if that will work or not for the bulb, but I wanted to try it. Below 4v, would the bulb be running on direct drive? If that is a complete fail, then I can use it with either 2x14500 3.6v 1000 mAh Li-ion cells (a little better runtime than 2x16340) on Strion bulbs, or 2x14505 primary cells.
And if the Streamlight 51101 bulbs just aren't going to work here, then I can always use them in your Fivemega D26 socket/reflector in your FM 2xAA body (C head), where they should be slightly brighter than a Surefire R30 lamp assembly. To quote Hickok45, life is good.