I would design the port on paper first, including the actual measurements for 150 sq inches, co lets say it ends being 15" x 10" by 10" deep well we know that 1,728 is one cubic ft so 15x10x10 =1500/ 1728 = 1.152 so 1.1cubic ft plus whatever the sub displacement is total is how much bigger I would build the box to account for displacement unless kicker already did that. I would call there tech support, it's free and there guys really know there products.