When designing a board a manufacturer can only accomodate a certain foot size range for any given size of deck. Stance width and angle will effect this range. Essentially, at your chosen width and angle you will need to exceed the boards width (with your bare foot) to gain leverage but not by so much as to cause critical toe drag.
Similarly each size in a given model has a weight range that will be able to comfortably flex the core and laminates while not distorting the shape unintentionally.
You will get the maximum out of any design when you are centerred in the weight and foot size range for that deck.