I ran my old VM on a siphon from 1992 to 2000.
FPS, cycling, and cold weather were never problems.
Ran like a dream EXCEPT for effeciency. I was getting around 400 shots per 20oz.
And on humid days, I would be ENVELOPED by the vapor cloud. Pretty damn funny... or so I was told. I didn't think it was all that funny since it seemed to make me a big fat target.