We start with 100lbs and drop down if we aren't getting bites, especially when we are marking fish. It's rare we fish less than 80 and typically we do very well on the chunk. The only time I have noticed the lighter stuff matters is when it's a day bight. Having a slightly heavier leader may result in fewer bites but when you get the right one you'll have a much batter chance of putting the fish in the boat. The odds are stacked against you catching a 200lb bigeye or a sword on even 100lbs leader nevermind 60 or god forbid 40lbs. Not saying it can't be done, but your not doing yourselves any favors.
More important than lighter leader, we have found using a long leader (10 feet or more), hiding the hook in the bait well, and then securing the sinker at least twenty feet away from the bait will make a difference in the number of fish you catch. The other thing that I think can make a difference is to stretch and straighten your leader before putting it in the water and try not to handle the line with your bare hands if possible.
Finally having a good hard working crew is probably the most important component to catching well on the chunk. You need to have people consistently throwing chunks all night and you need to be constantly working lines until its time to go on the troll. I firmly believe the harder your crew works the more fish you'll catch.
Pink has always been preferable to clear line. Sport Fish mag had a picture of many different lines under water, clear being the most visible. Smoke, blue, red, multi color, and especially pink were much more camouflaged.