Yes, but get on with the task as soon as you can get off the aircraft. It helps if you know where you're going; I don't know how well you know SIN and where the QF lounge is.

Personally, my advice would be to sleep as much as you can whenever you can, and not try anything clever about timing it. If you deliberately delay your sleep until after you depart from SIN, you might find that you only get about 5 or 6 hours before your body clock wakes you up in the middle of that sector, and then keeps you awake throughout what it thinks is the morning. I find that getting another 3-4 hours of sleep between SYD and SIN means that I get off in London feeling more like I've had a full night's sleep, even if my body clock then plays that trick on me.