Here are the specs for my new sonotube design: Any problems or suggestions? Adire Shiva MK3 Driver with 250W amp and 18"Diameter 27" Length Sonotube My net volume: 98L 4" port 17" = 21Hz = 20m/s @ 20hz, is that too fast? My cone excursion reaches 40mm at 15hz. Is there a way to reduce this through the amp? My group delay is 20ms @ 20hz. How is that? I was planning to have .75" MDF inside the tube and .75" MDF outside the tube on each end. WOuld that be enough?