You do not need to cut the bars.
If you are using the stock controls, you do not need new mirrors, as how they mount has zero to do with the bars.
The real issue is the locating pins that your control pods have.
If you keep them, you need to very carefully locate holes to be drilled in the bars.
If you grind off the pins, the pods will be loose, and be it tape on the bars, use of adhesive, whatever, you will have to do something to keep the pods from turning. The throttle side is the worst. If you grind off the pins and don't do something about the slip fit pods, twisting the throttle = twisting the pod ! Bitter first hand experience speaking. I used old school white cloth medical tape on the bars, it works great.
Oh, and if you grind off the pins, try to use some kind of wrap or taping to block off the switches, otherwise all that nicely ground aluminum will find it's way inside the switches. Again, bitter experience speaking - but at least I realized it before reassembly and cleaned as best I could.