I by no means am a CNBG expert, but have spent some time in FL where CNBG are native and southern NC where they are also native and I don't recall ever seeing a BG that didn't have the edging. Then again I wasn't paying that close attention to it.
CNBG also seem to have fewer lateral bands that are more pronounced along with a very different coloration.
It would certainly be interesting to study known pure CNBG populations and known northern BG populations and then study known crosses and back crosses.
