Usually carry my 510 with PCC. Since getting my JS, it's the only PV I need all day.
I've been cart free and dripping exclusively for the last six weeks. I've got the lights timed perfectly on the drive home from work to work the Prod and SB for dripping when at red lights, but I still don't like it that I drip while driving. I'm considering a third or fourth unit just for the car so that I can load them all up and just grab the next one when needed. We'll see as time goes forward.
2 charged 510 mega's is all anyone needs on the go
Have you checked out the new "Tesla Filter" that Janty might be coming out with soon? It's in their forum here on the ECF. It might be a good compromise for you when you're driving and don't want to drip.
I carry 2 batteries and 2 cartomizers. Nothing more.