I own two Bianchi 9R2s, the final production version of this Bianchi "upside down" shoulder holster. Images on this web site show Bianchi's fitting chart for 9R2 shows that it fits S&W's Model 19/66 2.5-inch barrel. My Ruger SP101 3-inch barrel fits these holsters. Do a search on this forum for threads on such shoulder holsters, particularly my handle and Red Nichols. Mr. Nichols is the creator of the 9R1 and 9R2.
To be clear: Bianchi 9R2 accepts Ruger SP101 3.-inch barrel (and, I anticipate, SP101 2.25-inch barre). I concluded this after repeating the "will the holster retain this revolver" test that Mr. Nichols used for testing any revolver model's fit. His test required three repetitions to be accepted. I repeated the test 25 times.
Holster retains revolver when used with Ruger's OEM standard grip with checkered wood inserts, and also with a custom boot grip (rosewood, no checkering, slightly oval around grip) whose fit is not cosmetically perfect. When affixed, there is a tiny gap between wood at "backstrap" and top rear of cylinder frame. It does not effect shooting. It is merely disconcerting.
Hope this helps.