The wicking in the single can be trial and error. I have found that leaving the tails sticking out where visible and not quite half way to the base is the place for me. I use rayon and the coil and shoulders I leave fairly thick while the tails I thin out around 30% or so.
The dual was way easier for me. And other than the 1 drop I have had no leaking at all.
Good flavor for me in both tanks.
eta on the single there has been seeping on the bottom of the cap. Placed an oring (from a 510 drip tip) around the outside of the 510. I will let you know if that works or not because I am still not convinced that is where it is coming from......could be seeping on outer edge where it is machined press in.