Update: I ended up trying out both ways, a 3" port with a box size increase to 1.0 cu ft as well as a 4" port with the box undersized at .93 cu ft. The 3" dual flared port wasn't enough port area, had some port noise. It would have been fine in a trunk, but in my cargo area I could here it. The 4" dual flared port was fine, but the box size didn't do the sub justice. That and the external port was excessively long. It seemed as if the box size contributed to a loss of bottom end. I ended up ditching the project all together. I decided I am going to go through a complete rebuild and I am going to pick up an ICON for the next set-up. This all left me with a brand new DCON sitting in a box with nothing to do, which I couldn’t let happen. So I decided that our new hybrid could use a sub. It took a little convincing of my significant other but she caved stipulating only that she wanted at least ¾’s of the trunk space left in its virgin state. I spent all day yesterday cutting, sanding, painting, scheming and came up with what’s in the pic. It is a 1 cubic foot enclosure, build out of ¾ mdf, covered in silver grey alligator fabric, with a 3” dual flared external aero port tuned to 33hz. It’s juice is coming from a Hifonics Brutus 1200.1 with the gain set by dmm at 34.2v, ssf at 31hz, low pass at 65hz. Yes, that’s a cap. I don’t usually use them but with the touchy HID’s in this car I decided to use it. That and it was sitting in a box collecting dust… I toped it all off with a coat of panther pink on the ring and port to match the emblems and custom calipers that are on order. Needless to say, I am extremely satisfied with the results. The sound is incredible for a $150 sub. This thing easily beats out others I have had at twice the price. My better half is impressed as well and that’s not easy to do.