2 x 8 is weigh to go, my board extends out past the rails side to side by 3 inches each side, I also add two chocks under the board which fit snugly inside the hatch cut out, drill hole in the middle for stap and your almost there.  I also added a line from the board, down to the keel strap and back up to the board to keep it from popping up(very important).  Finally a line aft to the stern cleats and one forward to the bow cleat.  Its worth it but take a few moments to find the Happy Spot fore and aft for the board and make a mark so you can repeat the trim quickly, used this system for years and never had a problem.

Not sure about the board.  We just use two lines with loops in the middle of each lin to balance the boat when lifting.

  Rear line goes to aft cleats on each side with the loop on the hook.

  Next put the loop from the lifting strap on the hook.

  Forward line goes to stanchion bases just forward of the mast then on the hook.

You can use caribeener style hooks on the ends of the lines or just mark the turning point of the line and tie them off.  Takes a try or two to get the right length for balance but once you mark the lines it only takes a couple of minutes to rig and stows easily.

Jean,

Remember that hull registeration numbers were put two places.  You know about the numbers on the transom but there is a duplicate set under the threshold of the companionway.  Thanks for asking the question because I have recently seen pictures of the J24 built after mine in the World races. 

Regards,

Ken Shores

USA 2273