Stance is supposed to be about shoulder width apart, but of course that's a generic average. The way I think of it is, if you go into a defensive crouch, you're probably at about your comfortable stance width. Too wide and your ankles and shins start to hurt, unless your bindings are canted. Too narrow and you tend to be forced to stand with straight legs, which negatively affects performance. At 6'4" on a 160, You may be too narrow even at the outer ends of the mounting holes. And that's the problem with buying a board based strictly on weight. If you're far outside the bell curve for height/weight ratio, your board may not be able to accommodate your desired stance width.
I told my kids, "Someday, you'll have kids of your own." One of them said, "So will you."
-- Rodney Dangerfield.