I use fluorocarbon when I fish dries. Since I'm using 5x, 6x or 7x it doesn't seem to impact the floating ability of small dries, size 20 is about the smallest I can fish and still see these days. To be honest I don't think I have any mono tippet spools left. I use fluorocarbon when I'm fishing both warm and salt water. The "dries" are larger and even tippets of 25# fluorocarbon don't impact how they float. Like John I use thread furled leaders for trout and warm water. Each spring I treat them with some type of floatant.