Here is what I recently figured out. I like concealing my 1911, but it can be difficult on a smaller framed person, especially in summer. So here is my suggestion.
1) Loose shirts. I like wearing Wrangler fishing shirts; the ones that are button up but you don't really tuck in and are made to pull moisture away from your skin. 1 size larger than you normally do. So for me, 6ft and 185lbs with thin stomach, I wear a Large.
2) Get a good quality IWB holster that has 2 connection points, and can be adjusted for cant (angle of the gun forward or back). I wear a Crossbreeds holster and have the forward belt clip on the top hole and the back belt clip on the 2nd to last hole. This causes the whole holster to be angled forward, thus the grip of the gun is more up and down rather than horizontal. That makes it easy for someone who is not as thick front to back to conceal a full size gun.
Practice doesn't make perfect, it make permanent.
When I hear a Liberal say "I can speak for gun owners because I own a shotgun" I just want to scream "Well I can speak for vegetarians because I like lettuce on my cheeseburger!"