that's interesting; i have a single coil 2mm ID, 30g, .18 ohms (10 or 12 wraps) and tried your settings: 440 and 40w.
When semi cool, the coil only goes up to 33w to heat up and then when warm/hot, doesn't go more than 10w (5 to 10w fluctutions) and vapor is not dense enough...
that's why i go...