Bamboo, I thought about that too, but I figured that it's not so much the string vibration that creates handshock as it is the limb snapping back into brace. Plus, no matter the length of string, the center will always vibrate most because that's where you're pulling it (there are not three parts on a string, only two, the side above your fingers and the side below, thus wherever your hand is will always be the peak of vibration). So having a dissonant vibration throughout the bow itself (as in one where the nodes don't line up with the nocks and riser fades) would not affect arrow speed or the energy being transferred to the arrow.
But yes, probably over thinking it, seemed like a simple idea in my head, but gets quite convoluted in translation to language haha. Guess I should just make one and see!