how close can a 4" port be from the back of the box?

[jeremiah]

^^^??

[Blove1991]

Dont quote me

But I say 4"....How much do you have?

[HAVINGFUN]

What ever the diameter of the port is the rule of thumb but if you can go with more then do it. Either way you will not be able to tell a difference for the most part.