If there is a clear definition of what is "concealed means concealed" in your state's laws, then any portion of the gun visible to the casual observer is considered OC. If the definition is not there, or vague, then IWB could be considered CC and thus may open you up to legal trouble if you do not have a CC permit. Of course, OC must not be unlawful.
I think this subject, what is CC, was discussed here on OCDO some many moons ago.....a little indian lingo there.