Leave just enough to time the rest properly, don't leave the length of the cord too long. I time my TT so the rest only contacts around 2 1/2 - 3" of the end of the arrow from the time the rest begins to pick up the arrow to the point where it's fully picked up and ready to launch. I'd start with tying your serving/clamping your cord stopper on the cable at your desired location, then slip the cord through the cable below the stopper, tie a knot, and time accordingly. When you get the timing right with a minimal amount of cord, burn the end of the knot and you're ready to shoot!