M_Boats: M12 is pretty great!

Took the new-to-me M12 sailing at the local lake.   I like it! It's super responsive and big enough for 2 adults.   Pulls with the Priusno problem.     All in all a fantastic little boat!  It's still got one problem.   Apparently there is a problem with the seal on the top of the centerboard trunk towards the stern.   It leaks at the joint between the fiberglass and the wood lid and there is a visible crack. I flipped it upside down (Try that on the M15 or M17 :-) and looked up where the centerboard sits and I can see the seal. Any suggestions on a permanent and or temporary fix would be highly appreciated.