I noticed an ad for a windsurfing board that stated the volume of that board in litres. Both Al merrick and Rusty Preisendorfer have said that volume is a very important component of a surfboard. Different volumes for different size surfers and their abilities and the size and types of waves they ride and their likes and dislikes. Unless calculus is applied or the board is designed by CAD, it would be very difficult to determine the volume. It might be a good measurement to add to the normal width, tail, nose and thickness numbers but how the heck would you calculate it?