can't speak for melbourne, but i'm about half way between there and sydney, and summer/autumn (nov-april) would be the most consistent- NE winds anywhere from 10-25kts 2-3 days a week, with a southerly every week or so to mix things up a bit. i've got a 16 and a 12 and find they do the trick (i'm 85kgs) don't bother during aug - october unless you like super gusty westerlies..