In doing some reading about this bike on the Kawasaki site and a couple of others, I started getting the impression that the cat is actually dual cats inside of the mufflers.
So, while doing some parts installs on my lift today I raised it up and sure enough, there seems to be no cat forward of the mufflers. That means that simple slip-ons should increase flow dramatically. It will also mean that those who have strict emissions tests will have to put their factory mufflers back on come testing time.
When you see a car, think of the stupidest thing the driver could do, then get prepared for them to do it.