if they're added at the same time i think they'll be fine. oscars are a schooling fish and usually dont mind company even introduced to another when its beenin a tank long term.Agreed with Joecoral, chances of pairing up slim, especially as there is no easy way to sex oscars also although Stitch will be introduced into a new teritory, there is likely to be fights between the two oscars (even if they were of equal size, much better to grow young ones up together).
Oscars are schooling fish? I think that is false...