One of the things that I notice about using a Kickport is that I don't need as much stuffing in the drum with it. Once I'm tuned up, it's really just about finding what works for what I'm doing. Right now, I have no stuffing at all and have an SK2 on it. The feel is excellent.
The thing is, no matter what, you have to like it. I love it. I can feel the difference and won't play without it. It's not an 18" sub, but, when air moves and the drum is tuned, it hits me in the chest much more than without it.
The other thing I've noticed is that cutting a fresh head to exactly 5 1/4" works best. No noise, no rattling, better seal and fit. Also, like I said in earlier part of this thread, when you mic it up ---- mic what comes OUT of a Kickport, NOT what's inside it. Adjusting nearer/farther and just listening to find the sweet spot makes everything sound so solid.
For what it's worth, I'm now on my 2nd one. Amazingly durable. The Kickport 2 is what I have now and I love it. Better fit, slightly less mush, less ring-y, I think.