I have use clark squid spoons for a number of years. I primarily carry them for spanish in case we see some coming in from offshore. I usually use the larger sizes. We have caught hundreds of spanish on them, along with some barracudas (some large ones too), blue fish, bonito, etc.
We use flurocarbon leaders. Sometimes we will put a 1 oz trout inline weight in front of the leader. We tested with light wire but got very few hits so we now just use fluoro. We generally troll them at 5 to 7 knots.
In my memory, I can not recall actually catching a King on one. Has anybody done so, and if so do you rig it any differently?