Another vote for a purpose built AIWB holster. The plain jane IWB (even straight drop) holsters do not translate well to AIWB and maximum concealment. I have a FIST #1K that I love for IWB with my G43, but when I try to AIWB with it, it does not work well.
The correct belt will also be critical to both concealment and comfort. Read the EDC forum, LOTS of suggestions there...