Thanks everyone. That is good information.
I balance my props carefully using a Dubro balancer. I think I have them about as perfect as I can. I don't know about the spinner. It is a Tru-Turn, so I think it is good. I don't know how to check or balance the the spinner.
I can tell that the airframe is contributing to the noise level because I can put my hand on the wing covering and the sound level gets quieter. Its like the monokote is acting as a drum head.
I'll look into the neoprene and Hyde mounts. Stuffing the wing panels with something soft and spongy might work.