If you take a look at this thread;

http://www.catsailor.com/forums/ubbthreads.php?ubb=showflat&Number=189124#Post189124

A guy had the same problem with anF18 which has a similar looking tang, if memory serves me. Once he realised that he should consult Nacra before chiseling off the deck, i think a repair was done from the outside!