Just kind of bumping this. I can't advise on this here because it is a topic/situation that deals with so many factors it makes my head spin. You'll have to get advice from the true pro's.

Meanwhile look into/read some of those past threads listed under "evaluating and adjusting fish poplutions". There have been many threads in the past that talk about larger ponds and the fish popution. Maybe someone else might have a link to one...

My only thought is what if there are larger LMB in there that you don't realize? They will just chow down on any new forage fish you add. Might need to stock adult fish to get the forage food chain going.