I'm really chomping at the bits to get this but have never owned a short barreled 3rd Gen model before. All mine have been longer. I know some of the 1911's in a 3-3 1/2" barrel have been problems but don't know about S&W. Are these fears unfounded?
I have also found that if you ditch the original followers, be they yellow, orange, red, or steel, and use BLACK factory 45xx followers, then you can use any generation of 45xx mag in any generation 4516. I called the factory looking for yellow ones, and they sent me black ones and a note saying "These are the current correct replacement". They all work perfectly.