As long as the pistol is protected by a properly designed back-pocket holster (full-counterprint panel), you should be able to carry your R9 in the back pocket without fear of damaging it. Even if you were to slip and fall on your "back side," I would expect that the only thing to suffer would be your
gluteus maximus, not your R9.
As John notes, the major issue with back-pocket carry is the comfort factor. Some like it. Others don't. Although, as I recently noted in another thread of the Forum, I usually carry my R9 in the strong-side front pocket (sometimes using a back-pocket holster if the full panel is needed to avoid "printing"), I've become accustomed to back-pocket carry and use it on occasion.
Good luck.
Caveat: All of the above assumes that the back pocket is deep enough to cover the rig completely. A flap or button closure can also increase security.
[size=10]Edited to correct typos and add caveat.[/size]
