I've got a subtank mini on a 20w, and love it. Yes, there's a slight overhang on the front side by the firing button, but it serves as a sort of thumb rest when firing it. I've included a couple pics below, including one of the tank on the 20w, as well as how I hold it. (sorry, posting on phone and can't link all that easily.) I've currently got a 1.3ohm build in the rba deck (8 wraps of 28g) giving a nice amount of surface area, and it performs beautifully.
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