But, there isn't a rule limiting the depth. There is only a rule limiting weight.
The boards should have less drag because of a reduction in induced drag not because of a reduction of surface area. Induced drag is caused by tip effects. By making the board taller with a shorted chord reduces the amount of induced drag.
My mistake, there is nothing about how long they can be. I was thinking that to stay in a box (for box rule) there should have been something about it, I was wrong.
I was considering the cord as the drag coefficient and said surface area, sorry. The cord on these things is very small.
