wow, *** never seen a festae that aggressive before, i mean, one of my LFS' had a breeding pair with angel fish lol, and yes, they were 100% festae, they were beautiful!
but whoever said it depends on the individual fishes personality is 100% correct, a perfect example is me keeping my flowerhorns and oscar together, my flowerhorns are 6" and my Oscar is 7", i was told by numerous people it wont work, and by the time the flowerhorn but 5" it would kill the oscar, well, guess who runs the tank... i had a 9" flowerhorn in there before as well, but my smaller flowerhorn was nicer and the big guy didnt take a liking to the new flowerhorn, so off he went.
i would still side with the trimac or RD over the festae.