Gestalt said..
Was also for light wind (front strap) and strong wind (rear strap).
On slalom boards they had 2 sets of front and 2 rear so you could course race. Front set for upwind, rear set for reaches
My first funboard, UFO , had two rows of front straps and three in a row at the back. It was sooo heavy and draggy that you needed the far rear one in heavy wind. My arms feel sore just thinking about it.