Howdy OP, welcome and thanks for posting.
It sounds like you've got a great pond, and as He Who Has Posted For A Year And Two Days And By Rights Should Be Tagged As Coppernose [otherwise known as Travis] wrote, you're very fortunate to have such a good population of fish in general and crappies specifically.
I'd be afraid to try to "fix" anything, for fear of throwing the whole thing out of balance. I suspect you've enough large predators, between your bass and cats, that many of your midsize crappies are consumed. This is often missing in ponds with crappie.....I'd be very interested in the thoughts of some of our more experienced folks, but it sounds to me like you've already got what a lot of us strive for.
