The main reason why folks dont keep plecs with discus is because of water quality - plecs poo for England![]()
I have been warned by several sites/suppliers that plecos (commons mostly I think) and ottos can be a problem with Discus. You have to remember that Discus feed their fry using their slime coats.
I would also not suggest Flyings foxes for a discus tank, they get big, are too fast and don't really handle the heat that well.