Use a heat gun. A hair dryer wasn't enough to get it hot to mold it.
There's a little nub on the outside along the slide. Heat that area & then from the inside push it out a little(only a little) that should ease retention. Same thing for adding tension, just push the nub in from the outside of the holster. It's really easy. But a heat gun should be used. You can buy a cheap one from a hardware store. I got mine from lowes for $15.