I'll talk to you KDog...

I read a thread on here about Lake Wendoree having some water & it's definitely big enough - pack your weed fin though.
Lake Colac always looks good, very open, and I've been keen, but never sailed there.
Pt Fairy (3.5hrs West of Melb) is a great spot with the Loch on strong offshore winds (NE-NW), and you can pick an ocean sailing spot for most other winds around the area.
Inland - Lake Hamilton, Lake Linlithgow, or Lake Bolac (about halfway between Ballarat & Hamilton).
If you're doing a loop (Ballarat, Hamilton then to coast & back along Ocean Rd or back to Geelong/Melb), come via Portland...there'll be a small number of us hoping for a sail over the weekend (wind permitting). Always keen to meet other w/surfers.