It does fit, u place the two pices on top of eachother (they are only 40 mm high, the man board is 50 mm outside = 42 mm inside). The space is 600x800x84 when folded, the two pices on top of eachother are 500x600x80. That leaves a 300x600x80 space and my plan there is to make box of wood or paper to store units, dices etc! 😄
It’s really too bad you didn’t make the side piece so that it would fit into the inner portion of the main board where the map is.
You could even make a simple cover to keep the pieces inside from falling out all over the place. It’s a great idea you have there though.