So far it seems I did the right thing. The past 4 days I'd say the aggression in the tank is at least 75% less now that the trouble making trio of zebras are gone. I still have two 5" zebras, but they have been in the tank from the start a year ago and are actually pretty mild for zebras. The rusties seem to be a great little fish so far. They seem to group up a lot and don;t cause any trouble so far. The first day the OB and Mbamba Bay male were chasing all the fish around, mainly because the balance in the tank was off because the three top fish suddenly were taken out. After a day though the Mbamba Bay male calmed down and now the Ob runs the tank, but not to the point of actully harming anyone like the zebras were doing.
So far so good, happy with the decision to trade them in. Just hope they went to a good home.