The 13.5 g was an estimate as the needle had wrapped itself around the end stop. Initially they thought there was nothing wrong with the aircraft, but next morning it had a distinct sag as the main spar had cracked. It sat in the hangar for a couple of years while they figured out what to with it and eventually welded some railway track to the main spar. Because it had been off flying for so long, when it came out again, it was the aircraft with the least overall fatigue on it so any high g sortie was planned to use that one!