You can do a box built like in this post with a port width of 2.5" with the following parameters.
Width= 44.00 inches
Height= 19.00 inches
Depth= 10.00 inches
Port Length= 28.99 inches
Vent Width: 2.5 inches
The only issue is that your magnets are going to be within .5 " with any box 10" deep with a port becuase to get the port lenght you need you will have to position the drivers in front for the second slot.
IE .75 (face wood) + 6" mounting depth + 2.5 (port width) + 2*.75 (port slot width and back) = 10.25!!
Assuming that the actual mounting debt is 6" -.75 (wood thickness) then you have .5" to deal with.. this is not ideal.