Property Management Recommendation Flat Fee or Commission Based

Hi,

I am trying to rent out my apartment in Southbank Melbourne, but it is proving more difficult than when I last leased it out.
Does anyone have any recommendations? What are their fees?
Has anyone had experience with flat fee managers? Was there a noticeable difference in the quality of their work?
My biggest cause of reluctance with using a manager at this moment is, my partner's work involves moving around a lot, usually around late January.
We don't find out where he will be until late September at the earliest. I'm worried, we'll sign a lease and then realise we need to move to Melbourne a week after they move in or something, and that the cycle for the lease will be off from here on out.

Thanks in advance.