Hi,
Like Emonty, I use the Vapornine turbo-cartomizer, and they're great at 6V.
They're at 3,7 Ohms, and the best hole for me are 1,2mm (0,8mm and 1,6mm works good too, but 1,2mm is better for me).
++
Your Voltage meter reads 3.7, but it is really 3.4~3.5.