I hate mdf! I know your supposed to use it, and I have used it before on my boxes, but I had these pine shelves so I decided to use what I had since I am on a budget. I did seal the baffles and all the seams inside and out with silicon. I put poly around the sub that came from the box I got it out of. It's fully surrounded. As far as the dimensions. I made the box with the space I had to go behind the seats. And I forgot how far those 6x9 screens stick out so I have to lean my seat up a little. The only other option I would have had , would be to stretch the box out and take up all the space behind both my seats and since I don't have a truck box yet so I still need storage behind my seats. I know it's not perfect, but is good enough for me right now. I am just wondering if I need to port that sub. Did you see anything on that sub site about it? I know some subs you don't port, but I always thought they sounded better ported. The whole box is 30" long 3 1/2" wide at top, 9"wide at bottom, and 12" tall. Oh and that's green beer for St Patty's Day!