The "lobster" treatment...
Fill a good sized pot with water and put it on a burner. While you're waiting for it to boil, take the holster completely apart. When you get a good boil going, throw the pouch in the water for 2-3 minutes. Wrap the gun in saran-wrap while the holster boils. Pick the holster out with a pair of tongs and grab it with an old towel, them shove the gun down in it. Let her sit until it cools- you'll be amazed at the difference. Worked like gangbusters on the holster for Peg's XD-40, although her's was so tight it took two 'baths' to get it right.
Re-assemble holster to paddle, adjust tension and loctite. You're done.