I have them on my bows too and I've quieted them up some with the sims limbsavers products. The small insulator strips I've had some success with on the arrow rest shelf for the rip cord arm to drop on. I also put another horizontal below the shelf and up high enough so the edge of the strip hits the Rip Cord arrow rest while atrest on it or when it falls. The strip is self adhesive and reduces the slapping noise along with felt moleskin on the arm.
I've also used some of the rubber foam on the back of a very thin mouse pad used some adhesive double sided tape to place it on the shelf. My .02