This is one of my favorite shoulder holsters because I can actually draw weak handed from it if necessary. The draw won't be fast, or pretty, but it can be done.
Here's some information from a gentleman who worked at the Bianchi plant years ago:
"all the holster designs in the 9 series were called Special Agent: Bianchi called its first elastic-retention upside-down shoulder holster the Model #9; the Model #9R with simple spring and internal recesses followed it; and the Model 9R2 that added the dual belt slots and the hammer spur guard completed the series. The latter is the best of the series for retention; the harness itself was essentially unchanged over the series."
As I recall, he explained that the Model 9 holsters (also called the "Bianchi Lightnin" came in different sizes to accommodate 2.0 to 3.0 inch barreled revolvers. I have a couple of 9R1 and 9R2 holsters that will accomodate 2.0 inch barreled J-frames, Colt Detective Specials, and a 2.5 inch barreled S&W K-frame Model 66.
Regards,
Dave