i have kept FHs(6-7"), 9"+ oscar pair, 8" GT, 5"+ cubans along with bichirs since they were 4-5" , my ornates were much smaller when i added them to the tank
now my sens are 10"ish, the ornates are bigger than my sens and still along with my FHs and other chiclids
had no problem at all, the chiclids kinda seem to keep ignoring them all the time never have i seen any aggression from my chiclids towards the polys
sometimes my fattest sen even tries to snatch a morsel tries to steal from my O and my O just swims away