You can set them up two ways IMO, both equally good:
Wide end forward on both front and rear strap (how I do it).
Or wide end forward on front strap, and wide end towards the tail on rear strap.
But as your front foot is always angled, and your back foot is not (well, sometimes angled the same way as the front one when radical), having the wide ends forward makes sense.
If you ride with your rear foot angled forward - you have either mounted the strap wrong, or should stand in front of the strap instead
But typically I one use a wide/narrow one for the front, and a symmetrical DaKine windsurf strap for the rear - then these questions are a thing of the past
PS: Nice comment knotwindy, as I would expect the same bull too...