Hello, Rhino,
We don't get down the line wave sailing in the bay but, on a 20-knot south wester and depending on where you are, the wave height can get to about 2m, although there's usually a lot of chop on the wave face. The wave period is only about 5 seconds.
We hope for big winds in winter (cold northerlies) and September/October (south westerly, but very frontal). One of my friends is a surf/wave sailor and he only has a wave board and his biggest sail is a 5.5m, but he seems pretty happy even when sailing in the bay (he normally travels to Phillip Island for the waves there).
Do a Google time/direction search from Mentone to Point Leo and Mentone to Torquay. Mentone is about halfway between Frankton and Elwood and Pt Leo (and surrounds) will give you access to genuine waves (as will Torquay). Both of these have surf/windsurf conditions.
Have a look here for past bay wind graphs
http://www.baywx.com/graphplot.html and have a look at the surf cams here for wave conditions on a daily basis
triggerbrothers.com.au/index.php?option=com_webcam&Itemid=183 (use the surf cam locations down the LHS bottom of the page), and
www.swellnet.com.au/, tab Surf Report and Forecasts, select Vic.
If you decide to come here, make sure you've got a job lined up and you'll need a 4/3 wetsuit for winter (our water temps get down to about 10 deg C in August).
Hope this helps.