I decided to try one of these conceal inner shirts, specifically this one from the NRA store:
I ordered a large because I read they are kinda tight but I think they need to be tight so as not to sag when in use. Its tight but the gun and extra mags conceal excellent, they are high under the armpit but not as to be uncomfortable. I am wondering how a x-large will feel and may order one just to see. I can see something like this being a good part of a conceal kit, I think more options for different circumstances is good.