The candle-wax procedure was a success. I (carefully) drilled through the glass over the hole, then used a small knife and a screwdriver to dig as much wax as possible out, the rest together with the little paper-ball was just pushed down into the brace. Finally I used a 1/4″ reamer to “touch-up” the nut. The harness will not be installed until the upholstery is finished.