If you have 72,000 points and depart from Perth you can do a PER-MEL-SYD-ASP-SYD-MEL-PER (SYD and MEL can be swapped around) JASA and receive 800SC with the double promotion. As mentioned it will cost 72,000 point and around $750 (based on the lowest JASA points fare) and you earn your 800SC and 16,000 FF points (if Platinum).
I've done this trip earlier this year but had a 3 day break in ASP but it can be done in one day...leave Perth at midnight and return at 10pm.
trouble is you'll probably gain 5kg with all the J class food