So, after much searching I have come to my conclusion as to what is causing the rattle (bb's in tin can sound) at higher RPM. It looks like the roller rocker arms have about 1 mm of play between them and the machined surfaces of the head. As you get moving, they skate side to side causing this rattley sound. I'm going to call Honda Canada and mention my findings, and perhaps recommend some spring washer mod for each side. That should cure the rattle.