help. built a sealed box too big. want to port it

ok, so i've built a box outta 3/4 mdf.. Dimensions are 27x18x10 and volume is about 2.05 cub inches. I basically built the box to fit snug in spare tire well not paying too close attention to volume specs. THe box is currently sealed for a single 12' sub facing upwards. I have an alpine type R 12' sub that i am going to use.


What i want to do now is port the box since i have too much extra air space in the box. Like everyone else, i want a tune of around 35 hertz.

Here is where i need opinions and help. Does a 4 inch tube diameter sound right with a length of 15 inches? Also where do i put this vent or port? On top and elbow the rest of the tubing toward the sub or away from the sub? Do i put the vent on the front of the box facing towards the cabin, or on any of the sides? How do i secure the the tubing down in the box? Note: THe box is built and carpeted already.

Also are there any good sites that sell these porting vents and tubing? Would i need more than one vent. Also are flared type vents the best? Any recommendations on a type would be helpful also. Thanks a ton

 

u mean 11.25 - 11.5 inches in length? And is it fine to elbow the tube because i only have like 8inches for height if i place the vent up top. Also does the opening part of the tube need to be facing a wall inside the sub box? thanks for the help