port size/length double check

Greetings.  I am very new to the concept of vented enclosures.  I have built a few sealed boxes in the past.  I am now trying to build a vented enclosure.  I have done the calculations according to what I have read/found/know.  I am hoping that you guys might be willing to offer your advice, and double check what I have figured.  Here is what is for sure:

The enclosure volume is 11 cubic foot after subwoofer displacement.  I am trying to tune to 40HZ. 

Here is what I figured it out assuming square/rectangular ports (right or wrong, I do not know):

1 port 6" tall, 20" wide and 9.33" deep should do it.

1 port 6" tall, 26" wide and 13.58" deep should do it.

1 port 6" tall, 28" wide and 15.03" deep should do it.

Like I said, I do not know if these are correct.  If they are or aren't, please let me know.  Also, what would be the difference in these?  According to the vent calculator I was using, any one of these three plus many others should do it.  I don't know.  Please help.  Thanks.

Ah, no, your calcuations are way off.  What calculator did you use?

A good accurate slot-port calculator can be found here.  Also, what sub are you using that requires an 11 cuft enclosure?  I like big low-Q enclosures but damn.

What is your sub and how many of them?

The subs are Diamond Audio D3's.  There are 6.  Right now they are on 2 JL Audio 1000/1's.  There will be a third one, so that each pair of subs will be on their own 1000/1.  The boxes that they are currently in are not the correct ones.  The have hit 149.2 and 150.0 on a Term Lab on two different occasions.  The dealer that sold them to me told me it should be way louder than that, and he is not really willing to help much.  He wants to be the one to build it, but I am not willing to pay the price that he wants.  I paid less for the subs, and two of my optimas than what he wants, which I don't think is fair.  I did not ask for any fiberglass, plexiglass, mirrors, lights, decorations, or anything else.  I just asked for an appropriate ported box to fit the 6 of them in my Tahoe (no third row seat present), and Therefore, I am lost.  The 11cft box is the only thing he really told me about what he would be building if he did it.  Sorry for my long-winded post, I just wanted to convey the whole story.

I am still unable to get the link working, but I believe, after looking at the web address that it is trying to open, that the calculator I used was the same one.  I'm not sure.  Here is the link to the one that I used.    http://www./help2/Articles.cfm?id=31