Interesting. I have a quantity of Vapor 4000 arrows that I got from the local archery shop. They were represented to me as having a spine equivalent to the 400 series Easton arrows. The shoot pretty well with field points, but bare shaft tuning has always shown a stiff spine (angle left) arrow entry into a 20 yard target. I'm kinda gathering from your post that they may, indeed, be a stiffer arrow shaft than the Easton 400's.