When I first started lifting I would actually make sure my shoulder blades were forward (I thought that was the correct posture). I did it this way for about two years before switching. My chest grew very minimally. However, my triceps and shoulders got a hell of a lot stronger. Even today I think my chest is lagging compared to my tricep strength. Not only that but I have had shoulder injuries on and off since then, at least partially due to that I'm sure.