Hi Damo, I am in the process of rebuilding a Mossie, one of the things I have done was replace the old cases and boards with some I bought from JK Fibreglass. As mentioned, these cases are moulded to the board. To fit them (after glassing the old slotss). They have a lip so that you can epoxy them so the underside of the deck. To make the gluing easier, I built a false deck out of wrc and glued the boards to that, then when it came to gluing to final deck, I epoxied and nailed the deck to the false deck, then routed out the slots. Boat still isn't in the water, however it worked quite well.