I haven't personally flown the route but PER-BNE is renowned for having 737s which means a much less comfortable journey in all classes.
I would recommend trying to route through MEL or SYD to get the better quality J for a comp upgrade. Flexi fares to OOL are good value ex PER and you could trying calling up to see if you can use the upgrade only on the PER-SYD sector.
In saying this, Flexis to OOL are more than $120 more expensive than savers but still cheaper than direct PER-BNE flights.
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