Joe,
if you've been from 6" to 9" without getting the bow to calm down I think you don't have an other choice then increasing arrow mass and/or adding (bigger) silencers to your string.
With RC's anything close to 8" sounds fine to start with IMO. I would not like to even experiement above 9" brace height.
I found from observation, cause I don't use those weights myself, that low poundages with theire thin limbs tend to make noisyer bows. Same for wider vs. slimmer but thicker limbs of same draw weight.
Can this cause your problem here?!