In the 2k18 version the chimney comes already attached via thick o-rings to the tank.
As @ricks said, this version has juice flow control which is operated by using the drip tip to turn the chamber. When you can see wicking - the JFC is open, when you can only see metal, it's closed.
Coil height also plays a big part in getting either more throat hit or more flavour. I prefer low to the airflow hole. But for those who like throat hit, raise it a bit. Here's my coil height:
This shows the different decks - 2k18 on the left, 2k16 on the right.
I use a 2.5mm id coil in the 2k18 - so maybe try a smaller id than 3mm.
As the deck is a GTA style, so your wick tails needs to go down a bit further than other RTAs.
Here's my 2k18 rayon
wicking:
I've thinned the tails quite a bit, and cut them to sit flush on that bottom ridge.
This shows also the coil height. It's only a mm or 2 above the airflow hole.
I use 28ga in my doggys, prefer the fast ramp up and these are 2.5mm id ss316l 5 wrap coils.
