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yes i mean a squonker so one space is for the bottle and the other one for the single battery, i was thinking about a single 18650 or 21700, which one is better for you?
Maybe i could do 2 versions one 18'' and one 21''

I have quite a few drippers that have sqwonk pins but I've never gone for a sqwonk mod.
For me a single cell wouldn't be enough as I vape SS316L coils that work out to around 0.1 to 0.12 ohms so its just too much of an amperage draw for a single cell. I think a lot of the DNA75 mods use a single cell - isn't the chip a max of 75w on that?
It all depends on what market you're going for. From what I've read, the DNA75 is an amazing chip - its just meant for lower power than my style of vaping so I haven't explored it further.
For the choice of 18650 or 21700; you've got more capacity and Amp rating with a 21700 cell, but you'll have a bigger mod at the end of it - it all depends on what market you're targetting and the requirements of the DNA 75 board.

That's all true then maybe would be better to use a 21700 on a DNA200

the market that i would like to target is the portable one, a box that you can bring everywhere you want.
I think that doesn't make sense to use a squonk box while you are at home becose at home you can easily do the normal dripping.

The DNA 200/250/250C chips are geared up for a minimum of 2 cells, but really shine with three cells.

The 250C chip will give max power of 200w with 2 cells, 300W with 3 cells and 400W with a lipo pack.

Maybe lipo is a good option to have high amperage draw while staying with the smaller profile?