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they won't make noise if you use artificial sinew and get them real tight...use two threads, two needles, the last bead on each piece turn on its side so the thread can go back through the whole group..in other words, all the beads stack on each other this way __ one underneath the other, the last bead goes this way [] so you can run sinew back through the whole stack, bring each needle up through your leather and tie them with a double overland knot and super glue the ends.
It will stay in place and not move. Those in your buddies bow look like 3 mm to me.