Don't know much about this particular boat. You can get an original brochure and drawing here: http://www.yachtbrochures.co.uk/grp.htm
I would think, however, that if you can get the centerboard out, it should be somewhat easy to add some shims.
Never seen any kind of user group or website dedicated to this model. Do know what the board is made of?.
Does anyone have information re the Duellist 32
designed by Alan Hill circa. 1979
Mine has a steel centre plate and is cutter rigged.
I'm having problems with the center plate rattling about in its
slot and wondered if others have similar problems or indeed found