They are certainly capable of doing just that.

You say you already have several generations of HBG established? That's not normally considered the ideal scenario, although there are reports of F2's and even F3's that are achieving good sizes in their own rights.
I'm dying to know... what do the HBG offspring that were hatched in your pond look like? GSF? Stunted? A high percentage of defects? Perfectly normal? What sizes are you seeing, and how do they stack up against the 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.