Altough I've caught my share of catfish, I can tell you that bigger baits will catch bigger cats. A few years ago caught my PB with a big frog fishing at night off one of the islands at Fitzroy. Also missed a big one at the mouth of the Mad / Ottawa with a big sucker. If you're using shrimps, put 3 instead of one. Sure you won't catch as many, but if you're targeting bigger fish, I find that's the way to go, and you might even hook up with a sturgeon
Just make sure that if you fish in the current, use a 2 , 3, 4 once no roll sinker.
Joe