new truck, asking for box design help

i recently got a 2009 dodge ram crew cab. asking for help on a box design. it will go in the middle backseat floor. the sub is a jl 10w7ae. needs 1.5 cu. ft. at 35.3 hz. the pics i put together real quick have the dimensions i have to work with. i do not want the sub firing up. if i have to extend the box up over the middle of the back seat i am fine with that. the top part in blue is offset for the console lid when open. any help is greatly appreciated.