I use rayon exclusively. For the fastest wicking possible you just whack half of the wick off right at the coil. Leave the rest just long enough to sit on under the deck.
For leak resistance you still cut half off but you do it even with the deck and the rest dangles in the tank. The idea being that all of the wick is blocking the hole and the rest is pulling up juice.
The wicking is still very fast and there's enough material to run the tank dry and vape for a while on it.
I rarely tilt mine but when I do it amazes me that I can watch a quarter of the tank capacity turn into bubbles in about one second.
To be honest my Cthulhu and Limitless attys have never seen cotton and I can't even begin to imagine using it in them. I doubt I could make the Limitless leak proof on it's side. I still have a .... load of cotton though. I did love platinum blend.
Yeah, having half sat on the deck and half feeding through into the tank is an excellent method, having the end of the wicks sat on the deck is the way to go, you don't gain anything from laying any extra along the deck on its side.
I don't get any leaking from the limitless with 3mm id coils and cotton running straight through the deck holes, i don't trim anything off the thickness. It did leak when using 2.5mm id, and 3.5id can be a little tight and choke itself, leading to dry hits.
Cotton is so much quicker to install, no faffing about tapering tails required and feeds the juice at a perfect speed for me, i find that rayon feeds to fast for its own good unless like i said, used in a small tank with small id coils.