Gotta take out the little crappie to have big ones in a small lake. The only problem with this is that if you take out most of the small ones as hard as these are fished, you may eliminate all the crappie.
The only way I could see that may help is to have a slot and not able to keep those that are from 10 to 12 inches and a max of 5 over 12 inches. I'm no biologist, so I am just guessing.