Im building a new enclosure it will take up most of my ext cab. The dimensions are 54" L x 21" H x 17" D. My subs will be sitting on top 2 SX 15"s I know with a 17 inch depth its going to be tight but I can get the job done. The enclosure will have two seperate chambers. I want to put a port in for each chamber and the chambers to sit on top next to the towards the middle. I dont know how long to make the board to go inside for the port and I dont know how large i should make the rectangular ports.