It was in the Jan/Feb 2003 issue.
It would be great for wets, beating an integral sink-tip hands down in several important ways. Essentially, separating the line and the weight are important bc they have very different functions. The LC leader is the fishing end and should be below surface currents, while the line is for getting that weighted rig where it needs to go, and then manipulating it. The line should be above the surface currents. Mending a floating line to a sunken leader is a joy.
I used mine primarily for big lake-run salmonids with both streamers and wets, both of which were #8 or larger, usually on a 6wt rod. LC leaders were so effective and fun to fish and mend to, that I also used them for resident trout in (as Brookyman mentions) streams med sized and up, esp in spring when flows were up. So I guess I used it in colder seasons. Summer water is less viscous and trout are more active. After summer showers, when levels came up, and trout left the wood work, they were active enough that they’d move for flies and I never broke out the LC.
When I used LC I swung streamers, wets, and sculpins through tailouts, or deep under undercuts and wood. Getting the fly down just an extra foot or two, and keeping it there, can do wonders. Man, just writing this I can actually feel big browns and steelies just CRACKING that streamer as it was held or slowly swum deep under a jam. RRRRIIIIIPPPPpppppp!!! If the fish is big enough, the line sings.
For lighter flows and/or smaller water, a weighted fly or shot tends to be adequate. I'd say LC is for places where fish are under, or unwilling to come up into, the heavier ceiling currents. It also works well for keeping the fly down on across current retrieves, which trout (and other fish) can find irresistible. I found 36 to 48inch sections most applicable. Shorter lighter heads were not much different than weighted flies.
I do not know what lighter (say 27 or 18lb) LC would do on lighter rods with smaller hooks. Worth experimenting I suppose. But I seem to remember coming to the conclusion that water is water (density wise –at trout temps) and you need some weight to cut it. So in my article I say skip the light stuff. In winter when water is cold and viscous, you’ll need 4ft of 45lb LC to get anywhere.
Nymphs? Some of the "wets" were buggy Flymph type deals that could be fished nymph-like. The lines across subsurface presentations can certainly blur. Leadcore spliced into leaders really shines for downstream or across stream presentations, although I did catch fish by throwing up and then throwing slack to control speed. There are more effective rigs for upstream I think though.