All I can tell you is that your flathead will be oportunistic when feeding which will also include eating your bass, bluegill, and channel cats if he can fit them in his mouth. I can tell you that largemouth absolutly love to eat bullheads and would probably do a better job in keeping your bullhead numbers down with fewer problems.
Here is a picture of a friend of mine from last year with a flathead he caught at a public lake near Lincoln. There are bigger ones in this lake than the one pictured. I would have to check the stocking records but I beleive the flatheads have been in this public lake for less than 10 years. They were stocked to help control a problem with stunted white perch in the lake.
