This is my setup for the vertical coil, 10 wraps 28g on a 1.5mm drill bit gave me 1.4/1.5ohms. The bottom hole is 1.5mm so if you make a coil smaller you are restricting your airflow. One trick I discovered, I don't leave cotton or hemp protruding, instead after tightening the chimney I take a sharp needle and stick it thru each hole several times. This seems to make small channels for the juice to absorb more evenly into the filler. You want it to work like a punched carto in a tank. You know you have it right when you see small bubbles of air form in the holes on each side after every few draws. You should not have to loosen the chimney or remove the Oring, if you get dry hits it is packed too tight, if it floods it is packed too loose. Packing is the variable that has a learning curve.
Since I only use VV/VW I try to keep my coils 1.3 to 1.5 ohms.
Have not found the need to increase any air intake, 1.5mm is plenty IMO. Just make sure no blocking in the complete path.
Here is my set up ready for dry burn and new hemp fiber. The top coil leg to pos. Bottom coil leg bent up to the post, this one can touch the sides as that is a common neg.
Filled with new hemp fiber and low voltage test