HELP Custom Box Design for Alpine Type R 1042D
 

Hey guys im new here just trying to figure out how to properly design a box for my sub. im using WINISD and got everything down pretty much except the port is confusing me, can someone just double check my measurements and tell me exactly what tune this box will give me ?
My box is HxWxL 12.5x18x14.5 =1.365ft3
My port length is 11" tall by 1" wide, and 20" long, i am looking for a tune of 32hz. Will these dimensions give me that?
i am confused about how to calculate the port length, it asks for box volume, tuning and HxW to give me the port length. but does it incorporate port displacement into my tuning? or is my 32hz set tuning still going to be 32hz when i add that sized port and the displacement is irrelevant to the tune.
Do you think this is a good box for my sub specs? i wanted to go slightly larger than specs.

Power Handling Power Range: 200 - 500 Watts
RMS Power Handling: 500 Watts
Peak Power Handling: 1500 Watts
Dimensions Mounting Depth: 172mm (6.8'')
Mounting Diameter: 231mm (9.1'')
Displacement: 0.050 cu. ft. (Front Mount)
Added Volume: 0.055 cu.ft. (Reverse Mount, Magnet Out)
General Frequency Response: 24Hz - 600kHz4

external box dimensions 12.5" x 14.5" x17.25"
Gross internal volume 1.3 ft3
vent area (dimensions) 11 inches2
vent length 22"
vent displacement 0.237 ft3
net internal volume 1 ft3