Some more mods:
The Voopoo Vmate is not bad. Incredibly light and really compact. It is so light, that it might even feel kind of cheap. But it's got a good chip, is compact, has nice feeling buttons (although made of plastic) and a nice screen. Won't be for everyone, but it's not bad at all imo.
My TAC21 also arrived.
First of all, this thing is huge and heavy as hell! But that's not too bad. It's still not as wide as many dual 18650 mods, which still makes it feel pretty nice in the hand.
Compared to the Double Barrel the Screen is quite a bit better, primarily because it has a cover over it, therefor I hope that juice-condensation won't be such a problem with this one. The Button is also waaaaaay better than on the Double Barrel. The battery door is also definitely an upgrade compared to the DB.
Overall I am quite happy with it, but there still is one problem. Not every 2x700 battery will fit. With the first batch the width of the batterys was a problem, which is not the case anymore. No matter what 21700 I tried (although I only tried the IJOY's and SC's) they fitted perfectly - atleast width-wise. With the SC 21700 getting the battery-door to actually close requires a huge amount of force. Even more than my DB needed at first. Using Fogstars 20700 on the other hand, which should in theory be just as long, fit perfectly and do not require an excessive amount of force to close the door with. IJOY 21700's need a bit more force, but still fit fine.
The TAC21 is not perfect, but I still like it quite a bit.