When I first started carrying, I carried with nothing in the pipe, mostly because I was very new to guns and was afraid I might do something to cause a ND. This fear was mostly with drawing and holstering the gun. At the time, I was using a Blackhawk Serpa for OC and an Alien Gear for CC. As I became more confident with the gun and learned to keep my finger off of the trigger and to check the holster as I re-holstered, I began to carry with one in the pipe. I only did that for about a month before I ended up buying an M&P Shield. I carry it with one in the pipe, but it's a bit different as it has an external safety that I also use. Completely comfortable with this. I practice drawing and sweeping the safety off several times a day and can do it quickly and without issue.