This is a very interesting topic. My Ps have attacked and killed one female adult convict (which was subbordinate to every other fish n the tank), but have not attacked 4 baby convicts, which were put in as food. These fish were originally less than an inch and 3 of 4 have grown to adulthood (1 is still a runt and I suspect it may never grow up) at around 3". These small fish are often the first to attack food that is placed in the tank and remain quite calm in the middle of a P feeding frenzy and get more food than they probably need. I haven't removed them from the tank because they don't seem to be causing any trouble and they clean the Ps left over pieces of food.
I have noticed that they do not "run" when being chased by the Ps. I think this is the most important factor in their survival. "Feeder" fish (or should I say, fish that are quickly eaten by Ps) generally attempt to flee when the Ps chase them, the Convicts (even when they were tiny) would turn and face the Ps and stay still, stopping the impending assault. I believe that Convicts instinctivly know that they are not fast enough to outrun a predator and that the best way to escape is to either stop moving or to face the predator. I cannot be entirely sure of this as this is the first time I have ever cared for convicts. I wonder if other south american cichlids behave like this when young. I'm glad my Ps aren't the only ones not eating cons, they seem to be a very popular P feeder fish. I got mine as cycling fish for another tank and dropped them into my P tank when the cycling was finished.