I've used Corbins on both my RC51 and my past Honda Superhawks, the VTR1000, not the Superhawk from the '60's. Humongous improvement over stock. I changed my countershaft to the 16T yesterday, then put a hundred or so miles on it today. The gearing change was a definite improvement. I think I may also go down one tooth on the rear and go aluminum for the back sprocket. It definitely is a fun little bike, but my butt is killing me!!!
After going to the 16T I compared the Kaw speedo to my Garmin eTrex, and it's just about spot on right now.
The thing is, all my street bikes have been v-twins, except for a Honda 919, which is about as close to v-twin power delivery an inline 4 can have. I'm more than happy working a motor between 4-6K rpm. The Versys is also pretty happy there, but if you want acceleration, it happens above the 6K mark. But still, a fun little bike.