I finally located a CS9 located in Kaliforniastan so I could buy it and did. It was in pristine condition, may not have ever been shot when I bought it:

CS9 - No SN.jpg

Very happy with purchase. Kind of wish mag capacity were higher. I have seen very positive reviews on the Magguts kits for the Shield. All the reviews I have seen say they work great and are very reliable. There is a +1 that only changes the internals: Smith & Wesson Shield 9mm MagGuts (+1)

And a +2 that changes out internals and uses slightly extended base plate: Smith & Wesson Shield 9mm +2 MagGuts

I am thinking that the CS9 and the Shield are pretty similar in size and both single stack mags. Has anyone has tried using the Magguts kits on their CS9 mags? If so, how did it work?