it should be fine i think, By taking the inch out of the box that makes the box 7ft^3 net on the inside,
so then i put 7 in the box for DESIRED NET VOLUME on the calulater,
then chang the port size on the calulator and it should think thats its useing just thicker MDF wouldent it and not mess with anything because the inside of the box is not changing it's always going to be 7