I am in the design stage of building a Home Theater sub using my Titanic MKII 12" driver and a Parts Express 250W plate amp model 300-794. I have been leaning towards the EBS alignment recommended in the Titanic manual. This is a 4.83 cu.ft. enlosure with a 4" diameter port, 15.2" long. I would like to use a piece of 18" sonotube I came across. Does anybody have any experience with this combination? How long should I cut the sonotube to get the recommended volume taking into account the vent and .75" of the 1.5" thick end caps being fitted inside the tube. Any input would be appreciated.