Moon, I wouldn't recommend making your bit smaller to do this, won't be very precise AND when you buy the kit, the install bit(s) come with a stopper ala the Switch Grip so that the depth is precise every time. This is important. Also, you want this depth in case you get a ball drilled somewhere else for some reason, and they install the IT, it will be the same depth as the balls you have currently.
SpareK, putting the system into a ball is dead easy, and just as fast or faster than the Switch Grip. Drilling the slug will take about the same time if you bought the kit or shop bought the kit, maybe a little longer. I would think install labor would be similar to a Switch Grip.
This system is very nice. I loved the Switch Grip, but the IT is better. Very solid in the ball, switches out just as easily. No worries about breakage. If anyone can break one, it would be me. I think my super tight thumb holes helped me break many Switch Grips. Don't think I CAN break one of these.
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