Just a word of warning, I visited my Westfield Doncaster in Melb today and for the first time parked on the roof.
I've never had a problem in any of their other car parks but on the roof there are some nasty speed bumps with metal caps.
I went over with next to no speed, practically stopped before taking the bump but still scraped badly and have some dints on the muffler below the front seats.
My car has stock AU1 pre update suspension, so 1 inch higher than other AUs. I've never had a problem on any other speed bumps.
This also came up a while ago here
Watch those speed humps!!!!