Gorgeous, george!
Theo's Theo-retical BG subspecies analysis based on % of body height above the centerline from the middle of the mouth to the middle of the tail says that a Northern BG has 50% of it's body height above the centerline, and a CNBG has 60% of it's height above the centerline. Based on printouts of the pics, I get a value of 60.6% for ewest's 9" example CNBG and a value of 54.1% for your nice catch of the day. This suggests that today's BG is a cross.
On previous crackpot analyses of mine, your BG have always measured in the middle; perhaps they have ALL been crosses between the Tyler CNBG and your Grandson's native transplants. Could that be the case?