Help with 187 Box

Just ordered my IA 187 12''

I was wondering if anyone can look over my numbers here to be sure that the box I'm planning on building will work correctly.(for a 12)

IA Suggests.

Ported 2 cubes - 2.5 cubes, 20 - 30 Inches of Port, 28-35 Hz

I have designed a box using this tool.

http://www.reaudio.c...t_Box_Calc.html

Width 28"

Box Height 16"

Box Top Depth 12"

Box Bottom Depth 18"

Wood Thickness 0.75"

Square Port Width 1.5"

Square Port Length 4" (seems to help tune it in)

This gives me.

30.063035251515 Hz

It may possibly be less once i put the sub in and account for the .09cuft of space that takes up.

I'm asking here, with these variables, Will this box sound good, and work well.

I also plan on cutting the port in the opposing side, so i can put the angled side against my car seats, and the sub facing the rear of the car.(Will this change the tuning?)

Any suggests about my placement of the port/sub will be greatly appreciated.