I'm currently in the process of reconing a 2004 RE XXX v3 15" woofer and haven't made the enclosure yet. I'm planning on building a 3.43 cu. ft sealed enclosure to house this monster, as my goal is more on the ""SQL"" side. The sub's displacement is .21 I've come to a design and have my cut sheets marked and ready to go, but I wanted to see if anyone could provide some input on if I should brace this box with a horizontal or vertical support? Does the enclosure absorb and vibrate this much with that back pressure to where I should brace the box? If so, what materials should I go about using? a piece of wood is fine? The box will have a double baffel, and be receiving about 1400-1600 wrms. I never actually found enclosure recommendations for this driver, but I am open to suggestions. I've only researched successful enclosure designs done by people in the past. Another question is polyfill..Should I use a lb or so to fool the sub into thinking its in a bigger enclosure? Please educate me. Keep in mind another reason Here's a link that helped me decide on an enclosure design: http://www.diymobileaudio.com/forum/member-reviews-product-comparisons/109015-2005-re-audio-xxx-15-review.html Keep in mind, I would go ported if I could, but I dont have enough space in my trunk. I have max like 3.8 cubic ft for a ported.