Vertical shoulder rig with an X-harness under a hawaiian/print shirt or suit jacket. The print on the shirt breaks up the gun's outline. If you get a gaudy enough one, people will purposely avoid looking at you.
The other concern is concealing in hot weather. Face it, it's hot here in Texas most of the time. How do you conceal in shorts and a t-shirt? Is an SOB holster right for that?