How does box wall affect port tuning?

Keep the basics in mind when you do the build:  end of the port must have space.  Leave 3 or 4 inches minimum.  The port opening on the outside of the box has to have this space, too, but that's a no-brainer because nobody would wedge their port opening against the car.  If the port is built as slotted ports usually are, with one of the port walls shared as a box wall, calculate the port structure width as equal to the width of the port plus the width of the extra wall.  As said above, the entire port structure has to be calculated as displacement.  The rest of the airspace is what WinISD is using when it gives you volume.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.