If I am trying to fill a 60"x (approximately) 81.5" opening, I can get two 30" bi-fold doors to fit the width perfectly (I would assume), but I'm not quite clear on the required height. The standard door height is 80". Does this mean I will need to put a 2x4 or the like across the opening to make the opening 80"? Or is the door height 80", requiring another inch or two for space above and below the door, as well as for the door hardware? Thanks.