I dunno.....but I sort of draw the line where those spoon "flies" are concerned. I know I am old and set in my ways, but it seems to me that a fly should ideally be made with feathers, hair and other natural materials. I remember feeling the same way when epoxy flies first came out and permit started to fall in greater numbers. I vowed never to use epoxy flies and to this day have not, although I think I have some bonefish epoxies that someone gave me and I'm too cheap to throw them away. LOL... But epoxy flies were the true catalyst toward me developing the Permit Rat in the first place. It has a lot of lead in it, but lead has been used to sink flies since the colonial days and maybe before then, so I guess that's simply my justification.
It's the age old question of when are we throwing jigs and lures, and not flies anymore? No doubt, once they're in the water and being retrieved, there's NO doubt as to their effectiveness. I don't (and never would) look down on those who choose to use epoxies and spoons, just as I do not look down on folks who use 20 lb. tippets, even though I never have. I believe some fish just weren't meant to be taken on fly tackle and that's just me. Sorry for the rant.
PS.....I am not alone in this assessment, but we few are all old and will be gone soon, so take heart.