board up on the hook and the boat can lurch mentaly in light swells. Drop the board to calm it down and it sounds like an army of trolls are on their way. As we're about to live aboard for quite some time I really wanted to nail this one.
The idea evolved rapidly from something overly complex to what I think is a simple and elegant solution.
Basicaly, a tap head silver soldered onto a piece of 1/4" brass plate, then well fixed on to the cb trunk just aft of the hinge.... see photo. Hope that explains the plan. So when at night I'll just screw the tap in a couple of turns to wedge the board quietly in place
On the inside of the hinge between the board and its' hanger sits a bit of 1/8 316 ss plate that is roughly the same size as the head of the board. So the stress is nicely spread on the board. The bolts are all very carefully flush to the inside, tapped into the pretty thick grp. I was thinking of maybe bracing the plate up, but I think in all it is a pretty bombproof setup. Will report in time on how it works in practice 
btw the white stuff is flowcoat from the po.
I've also added about 11Kg to the bottom... bit of a struggle to lift the board now, even with a 4:1 block
may have to take a bit out? 
The lifting point is obviously well beefed up.Here's the inner plate (on the wrong side, and the red line is where I cut off excess metal. I like the way this slots into the bracket and is locked in place by the cb pin
