Stuck On Dagger Boards Trunks - How Would You Build These? (plan photos inside)

Build them on a work bench, maybe over a jig if you like. I wouldn't have any wood inside the case or board. Keep it inert. I don't have an issue with the arrangement in the plans, which seems stout enough. I'd make the boards the weak link, so if you do bash a reef at 20 knots, your cases will survive, but you might need to make a new board.