You have to be careful with this mix its possible for it to work but you need to be prepared for the worst. I have two angels (5 inches) in a 100 gallon with 4 full grown 6" convicts and a redhead cichlid. They do rather well toghether. I have other tanks and the ability to move angels to another location if it didn't work out though!
I have another two angels ( 5 inches ) in a 55 gallon with an adult firemouth. The firemouth has nothing to do with the angels. The festivums give my angels more trouble, do no harm just a good chase now and then.
The larger your tank the better possibilty of it working, but again you need to be prepared for the worst and the ability to remedy the situation.