If you go for IWB style I strongly recommend you go for one with an offset clip (i.e., one that doesn't have the belt clip on top of the cylinder) AND offers tuckability (the clip is on a tab that lets you tuck a shirt over the gun and behind the tab, so all that shows on the belt is the clip.) The Bianchi 100 Pro mentioned above has the clip over the cylinder, and will be a thicker package inside your belt, while the RKBA has an offset clip and should be less bulky. I believe the RKBA is also tuckable, but it's hard to tell from the image I'm looking at on their web site.
You don't have to use the tuckability feature - in fact I use mine only rarely, as I tend to wear sweaters in cooler weather and untucked shirts in the heat. But on those occasions when you want it, it's there.