The most recent sets of class rules and drawings area available at the links below.
Note that Class rules are scheduled for update ahead of season 2024-2025. It is unlikely that there will be significant material change to the content of class rules, however Yacht Works is now understood to have ceased production of Castle 650 yachts. (having previously ceased production of Castle 550).
Yacht Works (Steven Douglas) is the registered owner of the design and therefore there is now a finite number of boats in both the Castle 650 and Castle 550 class.