I haven't scored any jacks this season on livies yet....jacks are suckers for any livie about 90mm long....mullet, herring, silver biddies especially.
I normally fish on on the bottom and one under a float that I drift as close as possible to the snags.
More fish caught on the bottom rig that under the float, but the float method is visual and gets your heart racing with the monsterous hits.
I use 4/0 or 5/0 mustad demon circle hooks only.
Wine corks painted white are the go.....put a slit in them and run the line thru the slit twice.....if and when you get busted up at least it is not plastic floating in bits down the creek.
This late in the season you will find more than half of your hits are small sharks.