false bottoms = added mass?

Hey folks  I've been thinking lately about false bottoms. Mainly about how possum boards deliberately suspend a dulcimer from the headstock and tailpiece, yet a galax bottom is mounted all around the edges. It occurs to me that the bottom board is sometimes considered to be the most freely resonant, hence the value of a possum board, yet a false bottom is attached at the places where the bottom board is receiving the vibration from the sides. In other words, it seems that a false bottom would steal vibration away from the bottom board. My first thought was that a false bottom should be as light as possible. Maybe then, it would make sense for a false bottom to be covered in holes and basically be the least wood necessary to keep the dulcimer off your lap. I would love to hear the thoughts of others about false bottoms and how to best utilize them for better volume.
Thanks
Nate