Did you get a dual coil cartomizer for the tank? Or are you just using a large single coil cartomizer. If you can find xxl single coil cartomizers that fit, those might be better.
A couple other tanks you might want to look at that also hold single coils regular cartos...
Submarine tank (mom and pops vapor)
Chibi tank (parkesvaping)
J-tank (electronicstix)
The DCT tank is a good tank for the price (I'm using one right now), but I find dual coils to be over-rated...the vapor production increase, in comparison to how much
juice you burn through, doesn't seem worth it. Plus you woehn't get maximum potential out of your lavatube. I reccomend you either find longer cartomizers that will fit onto your DCT tank (You just flip the tank upside down, so that the grooved bottom sits on top)....