Hey Razor..
I just saw your post in the Engines Forum..I don't think a 9X9 will over-rev a YS45, not at all.
I run 9X8's on the Duellist on OS 46VF's, and they have over a hundred flights on them, turn 17.4K or so on the ground, still feel new. And I consider the YS to be a higher quality engine.
So let that bad lad turn!