I always use my phone for GPS on the bike but I never liked the mount options i've used before - Installed a Quad Lock phone mount on my bars. I wanted something secure, that didn't look huge or obvious when my phone was not mounted. I even painted the base to match my grips / seat to make it blend in even more. It's just left of the clutch side grip. I ran an iphone cable under the tank and routed it along the other cables so I can charge and ride. So far I love this set up.
Yes Sir I did just cut the ends out of the grips.
If you install them on the bar first it's really easy to take a sharp knife and cut the grips using the inside of the bar to create a nice smooth circle. I have tried to cut grips before installing and it is much more difficult to get a smooth edge.
When you mount the bar-end be sure to leave a couple mm's on the throttle side so that the throttle still operates properly.
I use a spray bottle containing water and a couple drops of dish soap and apply liberally on the inner surface of the grip.
The water and soap act as a lubricant while installing and once the water drys (a few hours) then the grip stays firmly attached to the bar.
Good luck with your new grips.