I don't know where you can find the type XXIII plans but I submitted a post on 12/17/03 about a book I found on the type XXI. It has lots of scale drawings of pretty much the entire boat. The post has all the information you need to get the book. I'm a big fan of the type XXI myself. Good luck BSF
Sadly these plans (most of the Fritz Kohl plans) are no longer available in the US. Rocky Mountain Books was the one and only dealer in the U.S., but with the owners health issues they closed down several years ago.