Help with ported box for my x-18

[coh33dkill3r]

I have 1 x-18 in a 5.5 sealed box in my 09 nissan cube but hear that in a ported box it will hit harder. Don't know too much about building ported boxes but if someone can help with the design aspect I can build it myself. Max dimensions are 38W x 18.5D and my height isn't an issue. Wanting the sub facing up but don't know if I should have the slot port facing up as well or port the front bottom as I won't have the Clearance for the port to face the rear of the vehicle...