Plus, catfish are greedy, greedy, greedy. I've had oil catfish eat what must have been at least a fifth of their body weight, and they're just tiny little things. Willing to bet a redtail cat would gulp down several full-sized channels and a bass if it wanted to.
I'd be concerned about the redtail swallowing a channel cat and getting the channel's pectoral spines wedged into its throat. Might end up with a dead redtail.