You might look into joining the Catalina 22 Class Assn. Find it at
www.catalina22.org They have forums specific to the boat that will be useful both in terms of rigging, used equipment and issues with construction and maintenance. In my 30 years with owning and campaigning the J24, the Class Assn was a huge resource.
And, I agree with Joe on line size and block size. The 3/8 double braid that was a norm in the past is replaced by thinner, lighter, stronger higher tech line today. Only consideration on mainsheet size should be comfort in your hand as you will have it there a lot and if its a stiff/nasty line, it will wear out your hands. On my Beneteau 31 (310), my mainsheet is a 5/16 line and its plenty stout for the job. Smaller would eat up the hands. My mainsheet blocks are size 60's with metal sheaves. On the J24, we ran 2.25 inch (57mm) blocks as the largest
. Mainsheet/Spinnaker.
In the picture you posted, they have that mainsheet double ended so it can be adjusted at the bottom while you are sitting down in the cockpit and adjusted with the "head-knocker" cleat while you are sitting on the rail or a crew is on the rail and hiking.
