Could be a (head?) liner; but it could be the hull/sole shell. If so..... just drill a big hole in the upper layer and a bolt size hole in the lower. Stuff the void beyond the lip of the upper out... say....3/4"... and tape over the bottom hole. Fill w/fibred epoxy
/gorilla hair and once cured; redrill to spec. The traveler will cover the oversized, filled holes.