Im 5'10" 136 lbs. And the only place i can conceal is 12-2 oclock iwb, or otherwise known as appendix. Skinny guys like us dont do well at 4 or any other time for that matter. Lol
I can conceal a j frame, g26, or a m&p 9c.
I'm skinny (just under 140 lbs). Unfortunately, I do not have the height of the OP; I'm 5'8''! I have found that concealing a larger handgun is difficult, but certainly not impossible. I do not own a Crossbreed (but will get one at some point). During the months that I can wear a jacket, I often carry in a paddle holster. However, I use a Holster King. It works perfectly. Sometimes, I have to wear looser fitting pants or adjust my belt.
http://www.youtube.com/watch?v=HIhyhlO41_Q
Once you get comfortable enough carrying a gun that you OC on your hip like a boss, none of this will matter.