Styrofoam will be fine even if you need to cut the volume in half. Not an issue.
In my unprofessional opinion, the heat issue would be more of a concern. Long throw, high power subs (like a W7) generate a lot of heat. In fact, thermal power handling usually determines the overall power rating. I know that the W7s suspension can handle more travel than what is advertised. A larger box will help a little. If you burn the voice coil, JL charges a lot for a recone. You can just about buy my Fi Q12 new for what they charge.
Choking off the pole vent would really limit the amount of power you can apply to the sub. Suggest going with the W6 especially if you like to turn it up.
If you want something that is similar to (IMO, a hell of a lot better than) a W7, check out an Fi Q from Fi Car Audio. Their subs are not nearly as deep so it should fit in that box will no issue. Just double check the speaker cutout.
I wouldn't think of a W7 as a good candidate for an enclosure of this type because its so deep...or even a W6V2.
Last edited by bigjae1976; 03-24-2007 at 12:11 PM.