I've got a 30 ft Van De Stadt Seahorse. Luckily I got the original plans with mine.
You may want to look into the Van De Stadt book that is available from their website and elsewhere http://www.stadtdesign.com/English/book.htm
though I have no idea if they have anything on your design.
All they have on mine is the study plans on the CD (which having the full plans already didn't really entice me into spending up big on the book).
I was searching for information a while back about mine, and came up with very very little. Van De Stadt themselves appear to offer little or no support or info of their older designs- nor apparantly does any of their team answer any repeated emails about them (in my experience unfortunately).
You may want to try contacting them though, and hopefully you have better luck.
Would like to see a picture of you boat if you have one yet, and good luck with the repair.