I've got a Don Hume OWB also that I carry a P95 in (which is a relatively large gun for CC). I've found that the Don Hume hugs my body tight, almost as tight as the IWB. Is your belt tight enough?
Yes, it is a hunk of steel on the outside of your belt, so it is going to be somewhat bulkly; but, it shouldn't be THAT bulky. Like I said, the Don Hume hugs my body very tightly (and countours to it when I carry at 3:00). Try tightening the belt or getting a better belt (or both).