I stocked 100 HSB on 9-1-12 in my 2 ac pond with similar depths as you and yes, the ARE elsusive (in my pond anyway).
I do feed and up until this spring I could always count on catching one on a pellet fly (AM LMB food wrapped in panty hose). This is how I would "sample" my HSB for growth, and I always know when HSB are feeding by the way they break water to eat. I wasn't doing it often although, they're so much fun to catch I may have done it TOO often as it now seems it's just the LMB feeding on the AM LMB food.
Have they become hook-shy to feed?

I will order some Stubby Steves as an alternative just in case.
Otherwise I have caught them unexpectedly on nightcrawlers while pan fishing and on a tube jig while angling to eradicate BCP. All other means of angling for them have resulted in LMB (but I'm not complaining

).
Good luck and remember to post photos, and mouth gape measurements when you catch one!
Keith