You usually need to brace only if there are large areas that have no support. In my case, I didn't need to brace because the port pieces add a lot of support for the top and bottom panels, but if you have a larger box and narrower port, you would need something that holds the top and bottom pretty hard but doesn't affect air flow inside. Check out the cross section view of the JL 12w7 HO box, they have like 6 or 8 braces inside it and it still cracked from the power of the w7! This guy who works at a local shop here showed me his cracked box, it was unreal. He was running about 1500 rms to it and cracked the sh!t out of it!
