I wick rayon in practically everything as I like it better than cotton. In my Mutations I usually build dual horizontal coils. I put a separate wick in each coil and return both tails to the deck. I have occasionally built quads in the Mutations, and then I usually pull a single wick through both, but pull some slack in between them, returning both tails and the belly to the deck; an "M" or "inverted camel" wick. I have never had a lot of luck with Z or X wicks but, when I am building dual verticals for flavor I will use a horseshoe wick. With cotton, you have to be careful not to overstuff the coil. Cotton swells when wet and it you get the coil too full it will "choke" and not wick past the very ends of the coil, burning the cotton in the center. The cotton should fill the coil, but still slide freely inside it, without pulling the build stand or mod around on the table trying to move it. Rayon shrinks when wet, and thus the coils should be pulled a bit fuller. Rayon also wicks a lot better than cotton, and the tails should be thinned to 1/4 volume or so before returning to the deck. Really, it's hard to thin them too much. They'll wick strong with just a couple of fibers touching the deck.
I am testing a pair of Old Skool stainless mesh wicks in the Troy2 dripper-- it's build like a Genny, with the negative posts (which are actually the positive posts in that machine) close down to the deck and a tall center post in between them-- but I haven't decided whether I like them enough to go to the trouble. I also have a set of ceramic wicks I acquired somewhere I will try in the Troy2 one of these days.