Hey mate,
As A.dawg said bream on plastics landabsed in the Hacking aint easy. I have only caught a decent number and size using bait and burley from my boat. There are a few spots inlcuding up past swallow rock and also south west arm where i have had success although these are a little harder to access than the wharves (such as wally's or lilli pilli baths, etc).
I think if you are limited to fishing off the wharves or even to mainbar/bundeena then maybe change your tactics to going for some squid or whiting, jackets or even flathead. At the common wharves and at bundeena these are more prevalent and easier to catch than the bream. maybe try bait fishing rather than plastics. nippers always do the trick in the hacking. an old favourite of mine when i was land-restricted was to pump nippers at mainbar then fish off the end of the flats into the deeper main channel. this usually produced gud results with whiting and flathead. similarly, squid can 'always' (unlucky if you dont at least catch one) from budeena wharf or wallies at night on jigs. just make sure you use quality to increase you chances.
6lb fire and 8 lb leader should be working ok as this is a relativley light set up. if you still dont ahve much luck try 4lb line and 4lb flouro leader. sizing down has always increased my big hits but also increased number of bust offs too depedning on territory. i have found that the hacking fish are very sensitive to weight of tackle.
Cam