Left-hand, right eye here. I shoot rifles from my right shoulder. He should have no problem with this. For pistols, I shoot left handed and have no problem picking up sight picture 1 or 2 handed.
"Throughout history, it has been the inaction of those who could have acted; the indifference of those who should have known better; the silence of the voice of justice when it mattered most; that has made it possible for evil to triumph."
-Haile Selassie I