The RX200x style mods are a great form factor for accommodating 3 batteries and being very comfortable to hold. I still like my 2 battery mods for size and outside use, and my little 1 battery mods for travel. That last might not sound like the best approach, certainly for battery life, but that's when I switch back to low watt, mtl vaping for low cloud, stealth travel type stuff. A single battery can then last me well over a day when my use is dialed back to ~2 ml a day.