help with final calculations-cp24.jpg

Box will house 2-15" fi bl. According to the calculations i came up wwith it will be about 3.2 cuft tuned to 32hz. port coming out of the front will be 5" wide splitting into 2-2.5" along the back wall. if you see anything wrong let me know. external dimensions are 40" wide 24" deep and 18" tall. Will also have a double baffle on the front.