21700 kit installed, with WeJoyTechs excellent GT4s repro., With a Taifun "nugget" drip tip, to keep the height down.

One full tank, .5 coil and 34 watts didn't even move the battery level on the screen. Sure, much of that is Aspires budget chip, but the cell life will be much better, any way you look at it....size difference is negligible.

One extra note is that once the 21700 "wing" is installed, the battery tubes can be changed without removing the wing...which means quick changeovers from 21700 to 18650. There is no option with 21700 to have the "wing" under the battery cap, as the original mod comes...which does hurt the styling a bit, but functionally it is superior.