Not sure what the pre-loaded enclosure is tuned to, but my 2 L7's don't dip down too low. A metric ton of bass boost solves my lower output problem though.
I had 1 tuned to 40hz 4 cuft. I had 64 inches of port and a large flare on the end which lowered the tuning down a few hz. I murdered the lows in "put on by jeezy" u know, the ones that most people at the hangout cant hit,and hit the notes that mattered. go with it man, building boxes is 1/2 the fun, the other half is sitten back gettin the message from the bass you made. I actually only got rid of mine cause I was having ear pain after 3 days runnin on a rf 1000bd. good luck