Yoli,
My guess would be the larger bass simply aren't hungry. If you have the amount of forage in their your saying they are probably feeding non-stop at will all the time, not having to move more than 10-15 feet to fill their gullets.
We also have a 1/2 acre pond and our total stocking numbers between all species was less than 100 fish. Our bluegill spawned this year for the first time and fishing took a dump for the most part. we can go down around 8-8:30 at night and the surface lights up like a hurricane coming through, the larger fish simply have no interest in anything other than YOY ..
I agree with RC though, bigger bait = bigger fish. I would try the larger bait and go with something as loud and annoying as possible to peak their interest.
Another option is try to find a friend or neighbor with a fish finder and go out marking them, if they are there they can be marked.
1/2 acre 14' Deep. LMB, WE, YP, HBG, BG, Rainbows.
