i had a breeding pair of fenestratus and the male was the most brutal fish i have ever owned(even when not breeding)
he was very gentle with his female,but would kill any other fish.
at 8 inches he killed
4-red hook silver dollars
1-11 inch pearsi
1-10 inch black belt
1-6 inch green terror
3-5 inch nicraquense
so no i dont think it will ever work,i saw a list on the internet awhile back(maybe someone else has seen it also)that rate cichlid agression from 1 to 10(10being most agressive)it rated fenes as 8's and after owning several i would kinda agree,my fenes made every other large cichlid i ever owned look like guppies as far as brutality was concerned.
i use to think they were that way because they were a breeding pair,but i kept on of the male growouts and he killed my trimac(both were 5 inches and grewout togother)so i gave him to a friend(he now has a 120 all to himself)