Hi PT40, I have had several World Models, they all have the monofiliment line attached to a balsa stick accross the hole through the ribs, normally you would tie or tape the servo lead plug to the end of the line at the servo mounting position, then pull the wire through to the other hole near the center of the wing, if yours is broke or untied, take a string or fishing line tie a nut or small fishing sinker to it, drop the weight through the hole (nearest the wing center) holding the wing tip down and shake the weight through the holes till it gets to the servo mount, then use the line to "fish" the wires through.. hope that helps?
Bud........