Here is the custom sub enclosure I built to fit an Exile Big12. Its about the absolute maximum volume (1.85 cuft) I could fit under the dash of a 2016 23lsv with the 3 outlet heater. The angles were a real pain to get perfect and I still have not completed a carpet kick plate. I made it from baltic burch cabinetry grade ply wood and sealed the whole thing in Epoxy to waterproof and make sure its water tight. I also screwed and glued with gorrilla glue that expands to fill any of my poor craftsmanship gaps. I also installed an exile amp to match and the WS420. I built this in solidworks so if you want the CAD let me know.