I follow you...I wonder if general body shape might help determine the bias. Specifically, I think RES have a more streamlined appearance, with a projected nose, compared with a BG and their taller shoulders, and more "blunt" nose. I see BG x RES hybrids both ways, but I never thought to try and correlate the red, or lack thereof, on the opercular flap. I have some photos of BRES, I'll look back through them.

Here's one of ours that shows red prominently. Notice that it is more streamlined also.....


"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.