Here are some pictures of a small GSF. A lot of the pictures you will find for ID on the internet will be adult pictures. These pictures of young fish might help in your ID. The young fish tend to be longer in relationship to the height. As the fish grows it tends to get taller in relationship to length, but still not as tall as a BG.
This is about a 4" fish. I've included several different photos of the same fish because each picture shows different features better. One has the fins spread out better. Another shows the blue/green bars under they eyes better, etc. Note the coloration on the fin tips, especially the lower fins.
Here are a couple of links that might be of help.
100% Green sunfish JDFarmer GSF in pond Hope this helps
