HBG are not sterile, and if you stocked the HBG with BG, you could conceivably be seeing some reproduction there also. Can't rule out the possibility of some "pure" GSF, next time you catch a smaller one post a photo.

The fish in your photos appear to display excellent characteristics, I would guess them to be F1's.

"Forget pounds and ounces, I'm figuring displacement!"

If we accept that: MBG(+)FGSF(=)HBG(F1)
And we surmise that: BG(>)HBG(F1) while GSF(<)HBG(F1)
Would it hold true that: HBG(F1)(+)AM500(x)q.d.(=)1.5lbGRWT?
PB answer: It depends.