The only thing you'll find in the NRS is that a Concealed Firearm is one that is not disernable by ordinary observation. There is no case law or any other supporting statutes to help with the definition of what OC is. But if people can look at you and see your firearm, it would be my opinion that you are OC, and I believe it'd be an easy case to argue in court (if it ever came down to it).
I've OC'ed like that before. I like the way IWB holsters secure the weapon against the body.