FWIW with all my big coil builds larger than 2.5mm it is NOT less is more on wicking... they require massive wicking and I wick the cotton way tighter in those coils than I did in those back in the 2.5mm and smaller coil cotton days. I "manicure" the cotton if the tank needs that for them to work flawlessly AND don't have long tails down in my tanks.
I also really need to pick up some 4mm RxW XL to go with my 3mm. The 4mm would be the cats meow in some of my tanks.
Yip @Spydro as I found out this morning...
I really need to try RxW again... I have a small amount left after giving most of it away to mates who really love it... I have never taken to it but the thought of wick that lasts a month or more is really appealing... maybe I'll dig it out and try it in a Serpent.