Hey Milsy,
Check out
thewindmap.com/#-38.32792177372133,144.32842254638672,7I agree with Matt...Paynesville is quite fun...its surrounded by 270" of water so there always somewhere to sail.
It gets good seabreezes in summer (15-20kts).
Metung is also worth a look but it can get pretty lumpy with the shallowness of the lake and the fetch of the chop.
My fave location is a spot called Sperm Whale Head.....its a spit that sticks out into the lake only accessible by boat.but its a nice flat area to sail.
cheers,
mick