After some trial and error I seem to have got it right!
I'm not sure which of these changes has solved it, but the combination I've got is:
28g Kanthal 1.4ohm 2.5mm non-contact coil.
Coil is 1mm off of airflow hole
Coil is not straight across but rather angled across deck
I took the cotton sheet, removed the top layer and tore about 3mm width off
Cotton is touching deck base, just.
All working well so far.
I'm not sure which of these changes has solved it, but the combination I've got is:
28g Kanthal 1.4ohm 2.5mm non-contact coil.
Coil is 1mm off of airflow hole
Coil is not straight across but rather angled across deck
I took the cotton sheet, removed the top layer and tore about 3mm width off
Cotton is touching deck base, just.
All working well so far.