I have a USB passthrough with...wait for it...2000mah Kensington USB battery pack!! 5 volts is not much lower than 6 volts! I have been smoking the penstyle for coming up to a year and I know its a bloody good smoker. Its also quite cheap when compared to other less capable smokers.
I don't know what was up with your penstyle!
--EDIT-- forgot to mention you will taste the e-liquid with the penstyle