The boards are not screwed in place, they slot onto the groove in the centreboard case and locate in recesses around the mast step, spine and aft bulkhead. They are supported on moulded stringers that are approximately below the inside edge of the side benches. On top of these stringers are two location bosses, the same thickness as the boards, that fit into slots cut in the boards. Finally brass, or similar, turnbuckle hold the boards down onto the stringers.
I used a sheet of marine ply, 9mm thick and made the boards in one piece, I think cutting them, whilst making installation and removal easier, weakens the board and leads to them breaking around the bailer opening. Hope this helps.