If i remember right RE's box calculator isnt correct. What amp are you going to be using? An audioque 1200d is a good suggestion since it has a little clip light.
I think this would be a good 5 channel, ive considered putting that in the planes for the future.
http://www.audiosavings.com/products/5-Channel-Car-Amplifier/HIFONICS-ZEUS-ZXI60.41K-BEST-5-CHANNEL-AMPLIFIER-EVER!/ZXI60.4---1K.aspx
Thats nice, I wonder if my mom still can make those things. We are native american too, and she used to make them when she was younger i believe. Its a plus that your mom is into your hobby.
I would change the port width to 4 and the length to 20, have the port facing the rear. Would give you a 35.17hz tuning which is still pretty low i would say, and a port area of 52 and 12.83 per ft.