[Dusty]

IMO, the best combo for shorts and tee shirt would be a Shield in a leather (Taqua, etc.) appendix holster with a spare mag in a Desantis pocket carrier.
(Dry-fire the Shield about a million times to get the trigger half-way decent.)
Those Kydex holsters are rough if you're driving or sitting-they don't give.
You can get to a pistol in your truck with an AWB; hard to do in a pocket.
Don't be like Spanky and carry it small-of-the-back...