Does you're boat have a heater?
We built a box for a Wet Sounds XS-12 today to go into an 08 23LSV with a heater. The box had to be sealed because of depth issues, but when it's done, you shouldn't be able to see the sub. The sub will fire forward, but the flush panel will be spaced out and the sub will have grill cloth over it.
There's a few pics on www.wetsounds.com
in the gallery of what I'm talking about.