Soo, lemme get something strait, you said in a ported box with the port directly behind the subs the air would escape without pressurizing the box, I got that, and it would help to cause over excusing and such case mechanical failure of the driver...
But in a band pass box isn't it the idea for the sealed sided to help control that so that the ported side can more efficiently do it's job, with having to tune low to be able to play low without much worry?
So my overall point is with the subs that far away from the port in his sketch how would it not pressurize the space at all before it left thru the port? Even if it does escape some without pressurizing it to full extent isn't the sealed section going to still yet do its job in helping reduce the chances of mechanical failure resulting in a still yet more efficient enclosure than a simple ported one?
I'm kinda tired so words my not be as clear to you guys as they are in my own head but hopefully you get the point