help with enclosure design and my math

[spljim 10+ year member]

I wont a 1.75cf box tuned to 35Hz this is what I came up with tell me if it is right I found that a 11.75" port 3"wide and 37.91" long in a 1.75 cf box will geve me 35Hz so the port takes up .77cf of space and my sub taks up .08 I add this to the 1.75 cf box and get 2.6cf that is a box of 36" wide 13.5" tall and 12.35" deep my ? is the port Length is 37.91" long that wood be 9.35" for the front port but I dont know how long to make the longer port pece I know it is not 28.56" because you hafe to masher down the cinter of the port so can some help me and tell me what the other port length is and if my box will turn out right it is for a 12" 3002SPL //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

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[spljim 10+ year member]

I mesed up all redy the port is 12" tall not 11.75" will this chinge mutch or shud I make a new plan and the first port is 8.6" not 9.35"