you want like 14-16 inches of port per sqaure foot, that looks pretty small, why not a port in the middle but verticle and going straight back towards back of box, if it has to be longer you T the port in both directions Rt and Left and have it follow the back wall, you get way more port area and the port will be easier to build.
Try to model it up with a larger port and see. If thats gonna work for you, then go ahead, the vent mach is still green so porbbaly not have port noise- just my .02