This is how the current button position looks with the oxfords. Collar button and 2nd button undone. 3rd button is high enough to keep from showing too much chest. If the button position were lower, more chest would be visible. That said, This works really well on the dress shirts, as the collars are not anchored to the shirt like in an OCBD. So it may be possible on the OCBD's to move the button down a bit without sacrificing much.