Jacklines
I think a better alternative to jacklines on a boat like the C&C 24 (I used to own one and it was a great boat!)is to install a secure pad eye on the cockpit floor. If used with a short tether, it will keep you on the boat if you fall or are knocked down. Also, clipping your harness to a bolt at the base of the mast will also keep you on the boat if you have to forward in heavy weather. Traditional jacklines, run fore and aft just inside the toe rail didn't seem like a good idea to me on that boat since if you fall, you'll go overboard, and if alone, you are going to be dragged in the water with little chance of getting back on the boat. I think the best set up for small boats is something like I described above which won't let you get knocked off the boat in the first place.