Thanks for your thorough reply Lobo. Much appreciated. Is it normal for the holster to revert back to its too tight condition after successful stretching with the bag method for a couple of weeks? Fit was perfection after that. The gun was left in the holster without the bag afterwards and was too tight again after a week. Are you familiar with the Mitch Rosen product mentioned? How about a wax applied to the interior?
Break-in requires the full combination provided by wearing the holstered handgun for several hours at a time over the course of several days. This exposes the holster to your belt, your body profile, and your pistol in combination to allow everything to fully conform.
Putting the pistol into a plastic bag and stretching the holster for a week or two, then taking it out and leaving it to relax will not have the same effect as a proper break-in cycle of use.
I have not used the Mitch Rosen product (although I am sure it is every bit as excellent as their leather products), and I don't ordinarily recommend any treatment for a holster's interior. But in very stubborn cases I have found that a VERY LIGHT APPLICATION of wax lubricant to the interior can improve the draw. For this I recommend a light plastic wrap (Saran Wrap or similar) over the unloaded handgun, then a VERY LIGHT APPLICATION of neutral shoe polish or Johnsons Paste Wax to the plastic wrapping, then working the wrapped pistol into the holster. The wax will be taken up by the leather fibers at points of contact and remain there as a lubricant to ease the passage of the handgun into and out of the holster.
I must stress that this is a relatively extreme solution and should not be done on a regular basis. Again, we are talking about VERY LIGHT APPLICATION of WAX, not oils or other agents that will impregnate and soften leather, overcoming the forming work and leaving the leather limp and useless.
A final note to deal with 1911-style pistols in general: Things were relatively simple from 1911 through about 1980, with every pistol produced by every manufacturer (9 total manufacturers, plus subcontractors for parts) on government contracts having the basic requirement of absolute interchangeability of every part. Production tolerances were pretty much absolute within a certain range. A Colt Model 1911 US Army made in 1917 would accept replacement parts from WW2 production Colts, Remington Rands, Ithacas, and Union Switch & Signal pistols without a quiver. Then in the 1980's everything changed. All patent protections were gone, all licensing arrangements were gone, all military contracts were history. EVERYBODY STARTED MAKING 1911-STYLE PISTOLS, and nobody seemed to care about "mil-spec" dimensions. Different slide profiles, different dust covers, different barrel-slide lengths, different sights, different controls (safeties, slide releases, tangs, you name it) became the norm rather than the exception. There is no such thing as standard dimensions anymore. A dozen companies are producing 1911-style pistols in a hundred different varieties or more, not to mention the custom shops turning our infinite varieties to suit any whim.
In the shop I have half-a-dozen dummy guns for the various 1911's. In my personal collection I have 29 pistols dating from 1914 to present day. There are still many production pistols that I cannot match in every dimension or feature. Then there are the after-market parts and accessories to deal with. Calling a production pistol a "1911" no longer means very much.
Best regards.