Gnotuk in a blow is probably the worst place on the bay.
Not only do you have waves coming in from the bottom of the bay, but you get counter chop heading towards Frankston. Sure can mess you around!
On a positive note, if you can gybe successfully in a blow at Gnotuk, you’ll be able to gybe anywhere in the world.
As for locations, you might try Keast Park, Bon Beach (Williams Ave, then turn right into the carpark), Parkdale Yacht Club, Hampton Life Saving Club and Dendy Street, Brighton. Don't sail at Green Point in a southerly.
Hope this helps.