I don't care to have a giant battery... I find the 808 sufficient and I believe that was what the Mistic resembled. I actually think you can add 808 carts to the battery, but you need to use an O ring.
Um...an O ring? I use volt batteries with KR808D-1 cartos all the time...no O ring. They are refillable too. I also use Kanger KR808 cartos and V2 cartos They all fit perfectly. I've even used Elite cartos on the Volt..no problem, but they look a bit funny because they are big. ANY KR808D-1 threaded cartomizer or tank will work with the Volt. No adapters or O rings or whatever needed at all. They screw on...that's it.