Talking Rock or Surf
The type of trace you use depends on HOW DEEP THE WATER IS.
As some said, Leeries hunt mid to top water, very very rarely bottom. This is true.
A non return clip can be used, but should be used in water that's not to deep. maybe in the 2-3m water depth range.
If the water is quite deep your livebait will simply slide right through the action zone. Like in a channel or in a river.
A fish uses the top part of it's tailfin to swim down and the bottom part of the tailfin to swim up (or so it's said)
As was said cut the top piece of the tailfin (of livebait) off, firstly it cannot swim down, second it makes it slower, and third it attracts attention because it is now struggling to swim, this should be done no matter what trace you are using for Leeries.
But the couta clip still works best, works on EXACTLY THE same principle as a running sinker (the swivel part), meaning that the clip can freely move either up or down.
The clip with the cut tailfin is deadly for Leeries.
Don't use thick bite trace, .60 to .80 fluorocarbon or clear line is fine. You should go as light as possible.
It's normally a very clean but very brave fight, the leerie also fights in the upper part of the water column so your chances of getting reefed is very very small.
I don't use treble hooks, I have the stuff, they were made by the devil. 1 or 2 5/0 to 6/0 hooks are more than good enough, 1 in the tail section and one behind the head.