I wasn't trying to insinuate you were generally unknowledgeable, rather this is not your area of expertise. It wasn't based on your posting status, but rather the questions you were asking. If you really want to pursue this, there are some general guidelines. Look at what most SPL guys have to give you some clues. Large enclosures with tons of port area generally arranged in a manor to minimize cabin space. So, first this should tell you that you would want to avoid a high vent mach. High vent mach/port velocity will lead to compression of the air in the port, which will cause large amounts of port noise and reduce the efficiency with which the air in the port can oscillate. So you want to use a port with large area to reduce port velocity, but on the other hand if you go too large the mass of the air in the port can become too much for the driver to effectively utilize. It's a balancing act. Second, you want to create a "path of least resistance" for the air in the port to more or less reduce drag on the air as it oscillates within the port. Also, port design/shape will have an affect on the turbulence within the port, which is one of the reasons many people use aeroports, flares, and 45's or PVC in the corners of their enclosures and ports. To reduce turbulence. As for the enclosure, generally you want the enclosure on the larger side. Larger enclosure = more efficient enclosure with a larger peak at tuning. Yes, you want increased cone excursion as more excursion equals more air movement. Load a driver in WinISD and compare the cone excursion graph of various enclosure sizes of the same tuning on the same power. You'll notice as the enclosure size increases the cone excursion increases as well. For tuning, you will want to tune higher. You'll gain peak output and better match the resonant frequency of your vehicle. You're not going to be doing hair tricks with a 30hz tone, especially with your setup. It will be more in the 40's and 50's. Tuning high will obviously cause your low frequency response to suffer, but that's the trade off. From there, it's all about experimentation and what works for your subwoofers in your vehicle. Those are just basic generalizations. I still believe you are searching for a unicorn here, you don't have the basic foundation upon which those types of systems are built. But if you want to spend a bunch of time and money (MDF, glue, screws, etc will add up quickly, you'll need to build and test and build and test and build and test) to pursue this endeavor, there's some basics to get you started.