I've carried a SIG C3 under a loose t-shirt without trouble. One doesn't have to immediately go to a Rohrbaugh or other very small gun.
I've carried slightly larger guns, too, but avoiding printing under a t-shirt starts to get challenging.
OTOH, in FL, GA, and NC, my preferred method was IWB over a t-shirt or tank, under a loose outer shirt. That has worked quite well with full-size 1911s, N-frames, etc.