The purpose of IWB is to eliminate the need to conceal that portion of the gun that resides below the waistband. If you have the holster outside of your pants, you are not covering the lower portion of the gun with your pants. You might as well use an OWB holster (since that is effectively what you have).

FWIW, I carry a 329pd (4" N frame) in a Galco summer comfort. It works, but it rides just a tad high on my frame, and I would prefer a bit lower riding holster.