I have found that the farther back the baffle sits from the trunk opening the lower the system likes to play. And it is generally louder on the meter. But then you run into issues with getting enough enclosure volume. I have trunk walled several 15's in my civic and if the baffle is flush with the seat opening, it always sounds like ass. Recessed as far back as possible helps a lot, at least in my case.
1998 Civic EX Coupe
Incriminator Audio 6.4
B2 ES6.1i Tweeters & Silver Flute 6.5's
Tantric HDD12 coming soon