“Big baits catch big fish” and this hold true for fluke.  A six or eight inch sardine or smelt with a long piece of fluke belly is a killer for big fluke however many fish are not hooked because they bite at the trailing end of the bait and miss the hook.  When using large baits I always employ a double hook rig.  I snell two 5/0 hooks about five inches apart on my fluke rigs.  I put the lead hook through the eyes of the bait and insert the trailing hook somewhere near the tail of the bait.  When you drift or slow troll and a fluke chased the bait and bites at the trailing end, there will be a hook waiting for him and you will catch the big boys.  This nice catch of fluke to 9 pounds was made using double hook rigs.