This box is for one of my students, his goal was the loudest system in the High School. No Problem. (he did most of the work, I supervised) Submitted for your critique. Two PowerBass S-12D and Box with Internal volume 3.15 cu ft and three 3-inch ports. Tuning is between 40 to 42 Hz. Yes a little more port area would have been good.
Yes, its PVC and there is one screw in each. There is plenty of Caulk on the back side and I used a 3-1/2-inch hole saw, so the hole size is perfect. In Fact, the ports had to be tapped in with a hammer.