They are correct in saying that you should get the largest tank you can put in without sacrificing trunk space that you need. In my case, I put in a 40L (smallest among the choices) donut tank in my Corolla (lovelife) since this is the only size that can fit in. But I was really opting for the 60L tank. Too bad though the bigger ones cannot fit my spare tire well.

Does the vaporizer need to be overhauled regularly (like yearly or so)? According to the technician at Clean Fuel where I fill up, this should be done annually. He advised me this when he noticed during tune up that the rpm adjustment no longer affects the way my engine runs during idling and suggested an overhaul.