If your fishing strictly for flatheads, then the it needs to be alive. We catch them in a river in NC, and we will go to a farm pond, and catch a bunch of 4-6 bluegills, and put them in a bait tank, then go to the river. Those small bluegill are like candy to a flathead. I have noticed that a wad of nightcrawlers on a 5/0 hook will catch the smaller flatheads occasionally. We catch a lot of channels in the 5-10lb range on live bluegill also. The bluegills stay alive a lot better than the shad. Crappie work good to, but they die a little quicker than the bluegills.
There is no such thing as a cripple being too close!!! If so, you might never see it again. I'm not going to take that chance!!!