To mbbishop:
Thanks for this superreply, but I think that you don't understand me.
What I want you say, is to use FC, !!!onlyˇˇˇ in the last part of my leader, the tippet (40 cm aprox.) attached to the fly, not using the whole leader made of fluorocarbon. I'm agree with you that it would be prohibitive, for a good drift of the fly.
On the other hand, you say " Frog hair, IMHO, is superior to anything out there in the mono world. But FC now seems to be FC and one make's not much better than the other's".
What do you know about Frog Hair, do you really think that is the best tippet? Why? Have you seen a lab test with diferent tippets compared?
And what are you saying, that FLUOROFLEX PLUS or SEAGUAR GRANDMAX, is the same that other worst fluorocarbons?

Go ahead, mbbishop (and Jackster1), post the lab results.
In all cases, thanks for all mbbishop and regards from Spain.