I get what you are saying, and I don't doubt what you have experienced.

My experience has been thattwo arrows that spine the same but are of a different materialmay or may not fly the same. Centershot of the bow, how well within the bow's spine tolernace you are, difference in shaft diameter, material flexibility/recovery,etc. can make a difference. Maybe not so much with carbon and aluminum, but definately with wood. I have shot wood arrows almost exclusively for the last 10 years or so, tinkering with several different types of wood anddesigns--laminated,paralell, tapered, and barrel tapered shafts. Like I said, I'm no expert, but I do have a bit of experience with them. It's like strings (don't even get me started there!)--some bows just "like" some string materials better than another. Danged if I know why, and it can vary from one shooter to another, but it happens. Some of this stuff doesn't make any sense on paper, but it works all the same.

Chad