If you consider a paddle holster, take a good look at the Blackhawk Serpa. Even w/out a belt these things lock onto the pants and you nearly have to undress to get the holster off (takes a few practices). The upside of this is that you'll never have a pistol grip in your hand with a holster hanging off the other end (happened to me w/a lesser holster). Very positive and safe locking on the handgun w/easy finger button release. They ride reasonably high so it doesn't take much of a untucked shirt to cover it. Finally, they make these holsters to fit every barrel lenght of a model (3-5" barrel 1911's as an example). With care you can shorten the holster by an inch or so w/a Dremel and not effect the integrity of the holster. And if you're careful, it'll look like a good cut off job as well. The only drawback is that they're only made for a limited line of handguns. That said, my wife doesn't believe a handgun is worth owning if you can't match a Blackhawk with it.

Good luck