There is never such a thing as too much around here.. Or so i'm finding.. But yes, too much juice is a problem which for experimenters causes high expenses... As for the P91, I'd like to know myself so hope to hear from others.
But, I believe you are right, if it doesnt blow, immedieately, they yes, yes and yes for the brighter whiter longer. But life span is the question.. Lamp wise, check the LF specs and similarly estimate for P91 vs 90, as every lamp has a design voltage to account for sag. Matching and guessing based on these specs, you will get an idea what lamp is least likely to fail, and what will border on insanely white, with 4 hours of life....
And "if it can be done" is the uncertainty. May I ask, what body and head were you hoping to use?
I like the P91; I use it in my Wolf Eyes 2x168A extended Sniper. But if I weren't so dead-set against bipin bulbs, I'd use the 3x168A Stinger by FiveMega with an axial bulb. I owned one briefly; the beam was wider and brighter than the P91's. Problem was, the pins didn't seat well; the light would mysteriously turn off, no matter what solutions I tried.
Sorry I can't answer your question but I can offer this; I run the P91 off of 2 of AWs 18650s and it runs very bright and white. I don't know how long the lamp will last since I'm still on my first one. I'd hate to say it will definitely work without having first hand experience but, for my set up I wouldn't be surprised to get a little less than average bulb life due to the overdrive. It is a trade-off I'm willing to take since I will be spending less on batteries. I just can't see too much of a difference between the 18650s and the Cs as far as actual voltage to the lamp. Perhaps if you charged them to 4.1-4.15 instead of 4.2 a little safety cushion would exist...??? I've run the P91 with the 18650s at 4.2 each hot off the charger with no problems.
