Never tried IWB as I always thought it would be to uncomfortable but he other night after cleaning my 5 " 1911 I thought lets see what its like so after making absolute sure that it was clear I stuck in in just behind my fat hip and thought wow not bad so I sat down and again wow not bad , moved into different positions and the same thing. Now I am looking for a new holster and boy there sure are a lot of those to pick from!
I'm a recent fan of Rocketman holsters for IWB. Dunno if he makes 'em for 1911s though. Either way, it's worth a glance at his site.
http://www.rmholsters.com. The IWB holsters don't look like much in the pics, but they're very comfortable with good retention and fit. And mine haven't slid around at all on my waistband. (I have two, one for a compact, and one for my full-size)