Been along time since I joined a disussion, always busy lol....
I liked this thread, so as a breeder here is my opinion.
Selection, this is the key word. F3 should be better than F2 should be better than F1, if not; you are doing something wrong. I am talking about the avarage appearance of the pups. By selecting the best you are aiming to breed the traits that are pleasing to the eye and pass them on to the next generation, which after a few generations makes a ray wickedly beautiful.
The right combination of male female is important, mix it up, try new combos, breed what works. And select again.
Pure or Hybrid.
I do it this way:
Pure Lines: Species are strictly separated from other species, one male per tank. I know the father, I know the mother. I know the lines back to the wc parents.
Hybrids: Go nuts, just be honest about it and don't try to pass it as pure bred. A nice ray is a nice ray, hybrid or not.
Conclusion: Don't pay more for the label F3 pay more for the F3 that knocks your socks off!
P.S. I really like classic looking rays aswell. A simple good looking Henlei to me is perfection.