Here's my reasoning (and if I'm off base, someone let me know):
The FHM will be eaten rather rapidly. I don't known if they will have a chance to reproduce or not.
If the BG that are stocked are large enough to avoid predation by the LMB/HSB in the pond, then they possibly could pull off a spawn or 2 this year, providing food in YOY BG.
If I could, I'd stock both FHM and BG. FHM would give the fish something to eat now, and take some initial pressure off of the BG.