Off topic from Sean's great bike build, but well there you go, I didn't know Kerker were owned by Supertrapp, you learn something every day!
I've got at least one Supertrapp muffler out in my garage, I had it on my Triumph Rocket III before I installed the Jardine "Big Boss" pipe, because it kept coming loose and wanting to be launched offa the header pipe, but I've had them on much less powerful bikes like CB750's, and they're an interesting design.
Ken from "Megacycle Exhausts" here (no relation to the cam people in the US) told me that Supertrapp mufflers were sh1t, were heavy and didn't make any more power than a stock pipe, but for someone less technical and more hillbilly like me, it was fun adding/removing plates to make the note that suited me the most. Even my "Seat of the pants dynamometer" could tell that there was no big power increase by installing one, but they are a cool piece of kit, regardless.
How they've stayed in business for the best part of 50 years that I know of, is beyond me, but marketing is what makes the world go around, so I'm sure Supertrapp will still be selling their "special" mufflers for time immemorial. I might put one on one of my next builds, just for fun.