On 3 fresh 123 cells you would be pushing a little past the upper limit of the EverLED and might damage it (fresh cells can put out 3.2-3.3v per cell).
However, folks around here are always looking for a light to use up their "spent" 123 cells after they don't have enough juice to run the high powered lights. I have been using a 2C/3x123 modded Mag with an EverLED for just this purpose. It works quite well. I sputtered the stock reflector for a cleaner beam, and did the usual 3x123 mod (PEX pipe, Duct Tape and a shortened spring). Runs nice and bright off of cells that are dim and orange in my PM6.
Aloha, iG