I'll check up on the orangs next time i go there my best bet though would probably be the oldest female, she has many features of the two subspecies. I forgot her name though.
Is it Kiani? If so I think she may be 3/4 Sumatran as her father was a hybrid too. From memory the original hybrid(s) at Melb were twins(Kiani & Kembar) They looked more like Sumatrans as babies, having light fuzzy coats.