I have the same set up on my Kyosho Zero, and no flutter at extreme speed (YS 63FZ). The elevator does have some play in it, but the play is not enough to cause flutter. Check your horizontal stab to see if it flexes. My buddy also has a Kyosho P-40, and bad wood was used in the horizontal stab. It flexed and vibrated so much that the covering cracked and popped.