Okay, so I get the following box plans from a free box calculator that someone mentioned before.. So I planned on making it. But then I downloaded WinISD to check those calculations... So I put in the plans from the online calculator, and it tells me that my tuning is at 48Hz. I was aiming for 40 So anyways, WinISD said that for a 40Hz tune in my box, I would need a 30" port length, my question is, can I just add to the port wall to make the box correct? I already have a lot of my wood cut out... What can I do to get the tuning correct?