I'm trying to design an EBS shiva using 20-inch diameter sonotube. I'm trying to avoid porting out the top because I'd like to have the option of using the sub as a small table. If I have to port out the top, I can always use a "baseplate" on the top, but this adds a good 4 inches to the height. I'd like to use an FP4 flared port kit as the adire spec calls for, but this page (http://terryctheater.tripod.com/shiv...bum/page1.html) makes me wonder if I'll be able to make it fit along with the driver on the bottom plate. If it will fit, it's certainly going to be a close fit. But going up to a 5" port isn't feasible because tuning to 18 Hz would require the tube to be too long to fit comfortably inside the tube. I think there would be about two inches between the port opening and the endcap. I've read that you need at least 3. So if the port opening on the bottom is very very close to the driver, and the edge of the flare is very very close to the tube wall inside the sub, am I still okay? I'd like to save myself the 4 inches, but not at the expense of sound quality. Thanks!!