i have 2 12" kicker cvr in a ported pre fab box. i was told that if i make a good box itll give me 6 0r 7 more db. it has to fit in the trunk of my contour also. my current box is 13" wide x 16" deep x and 36" long. its ported in the middle of the box with 3" wide port. my trunk opening is 39" wide and 19" tall.any ideas?}