I've added three pics to my album (in the wrong order) for my chart table. I wanted something cheap which didn't take up any room. I've taken 6mm ply and made it long enough to span the cupboards, and then carefully cut out slots so that it sits over the hardwood rails. It's also scribed around the compression post. Underneath is reinforced, but I may yet add a hinged prop to sit on the keel housing. I may add an edge lipping to stop charts and books sliding off in a blow.
It's very light weight, and is easily stored when not in use.