I am of slight build and unknowledgeable of shoulder holsters. I do not know whether there exists a harness that can be used with my Bianchi 9R2 upside down holster that spreads the weight of holstered revolver to more of my shoulder(s) and upper back than its OEM harness. Or does there exist a harness that can be adapted for use? Adapting an existing harness can be done by my "leather guy" in Missoula - that is, if adapting is the best or only available option.

The OEM harness places holstered revolver's weight entirely on one shoulder's trapezius muscle. My loaded Ruger SP101 3-inch weighs about 33 ounces loaded. And this loaded weight is significantly less than the loaded weight of an S&W Model 19 2.5-inch barrel in the same Bianchi 9R2.

Good luck with that. The weight has to go somewhere and gravity says that is straight down. You can spread that weight out over the biggest possible area, which should help in the comfort department, but that's about all. A custom leather craftsman should be able to help you rig up some sort of improved harness that is wider and maybe something that fits the shape of your shoulder better than the factory harness. It's worth a try.

You have persisted in this one :-) Now that I grasp what you're wanting, get or copy the ultra wide harness that both Alessi and DeSantis use/used. They depend, tho, on there being an ammo pouch on the offside.

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The Holstorian

Sometimes I leave persistence yards behind me. I've bought two 9R2s - one a back-up because they are long out of production and scarce. I've confirmed they work blandly and uneventfully with SP101 3-inch.

Now I just need to get holstered revolver as comfortable as possible, hoping/anticipating that will be comfortable in my "absolute" sense.
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I wish I had a grasp of what text-based glyphs mean.