Get a scale, preferably the electronic type, and tie loop on each end and test the strenght of your line, if its not in the area of the listed pound rating, youve over heated it in the trunk, or its a poor quality company.. I like reo… I was told Flouro carbon is for under water, mono is for on top… Ill bet you can use number four flourocarbon under water and the fish still cant see it… What the finer tippets would be for in my estimation is for lots of action.. This can be done by putting the fly on a loop… ..dave