I was actually thinking of a 10mm for a simple portable one hitter approach.Air flow is a big factor. The Zion heater tech is beastly. Take it from me, i have the Powerhouse here and also tried a single battery 10mm i called MicroZi. Using 10mm or even 14mm is a little limiting considering the power under the hood. I could maybe liken the 10mm or even 14mm to getting that new Porsche 911 Turbo S and only kicking it to 55 MPH in the city. You could make your way to your desired destination, but it isn't a whole lot more fun than driving the Buick Regal around town (accept maybe the ladies would like the Porsche more).
Although the 18 is probably the most versatile in terms of usage... I'm thinking the power is good enough to do a tiny load.... If not maybe the vaporgenie oil pad could be used to tighten up air flow as filler... Would that work in this/Zion? Or would it fuck up the stem being able to fit properly?
http://vaporgenie.com/liquid-pad-liquids-oils-waxes#.Vg1UdXPD-v0
Just thinking out loud.. I probably won't be buying any more vapor gear until I get my career settled.