Hi Rick,
I have used metallic red on big pheasant tails for trout, from Christmas tree icicles, and done well with them, but have no experience with red for warm water.
When I was in Kansas a few years ago, at the shop where Bluegill 222 worked, he showed me the nymphs Joe Hyde liked, and they had pearl flash back material. The nymphs did not have one moderatly wide strip, but instead had 3 or 4 very narrow parallel strips of the flashback material making up the flashback. This made for a very subdued flashback appearance, unlike something like silver of gold that will immediately reach out and grab your attention.
Regards,
Gandolf