i want to make a sealed box, does it matter what the dimensions are, as long as the displacement is proper?? its supposed to be 3 cu. ft, so any length and depth, as long as its 3 cu. ft?

also, does it make a difference if the back is slanted, or does it have to be a square? i would want to slant it so that i could push it as far back as possible in the trunk.