I have never had a rib problem with any SxS Beretta I have owned. I am not an expert in spoting a hot blued gun over a rust blued one so I am probably just lucky up to this point. My SxS collection ranges from a 1933 16ga mdl. 1010E to the 1970's with the GR2 and 426 in 16ga. I also have a couple 20ga's with no problems.
Best,
Ron