There are going to be a ton of pre-made mods available using the DNA 200 in a few months. A little patience and the options will abound.
In the mean time, I hope to finish making one (or two or five lol). And the first one will use 3 18650s. My planned form factor for the first one is basically a little taller and a little wider than the height of an 18650 and about 22 or so mm deep. Sort of a square with sides a little longer then the height of an 18650. Yes, I have big hands lol. I have seen a DNA 40 (or maybe it was a clone?) made in this shape and I like the look.