I'm testing mine just now and for best flavour with dual coil, put the coils as close to the side air holes as you can(baw hair away from them), single coil put the coil above the bottom air holes as close as you can get it.
I used a light at the back to make sure the coils weren't touching the deck with both single and dual. As for wicking, place the cotton on top of the juice holes and not inside them.
Coil legs length using the coily, mine where 3mm ID Aliens from TKD Coils. single 5mm. dual 4mm.