Building a enclosure for a guy I work with. Its 8cft and I have a 10in flare port I made awile back. Its for a couple TC9 15s, each will be getting around 1200 watts from a Kole Q1-3000d (have a couple more in my sale thread ) According to PSPs site it needs to be around 15" long to tune it to 53hz. Does this sound about right? Will be taking pics as it built after design gets the ok.