I also found this:
http://www.csxinfo.net/427cobra/streetcar.htm
According to the description at this site:
"E) This car also has the wide rear flares, or "wide hip" body. Notice that the rear wheelwells are slightly flaired. The narrow rear flared cars or "narrow hip" had no flares, or only a small lip on the rear wheelwells. "
They are talking about CSX3342, there are also some pictures of CSX3111. You can
Compaired to the S/C or comp type rear flair you can really see a difference.
Rick