There were several DC8-63/73 freighter loading incidents where the aircraft sat on its tail. I was almost involved in one. The rule was the forwardmost pallet position was loaded first and unloaded last to keep the CG forward of the critical point. I was changing a main wheel on a Flying Tigers DC8-63F that was being unloaded and went to the cockpit to release the brakes and noted a large step up to get into the cabin and on entering the cockpit the stick shaker was operating meaning the nose gear was in air mode. Sure enough the nose wheels were off the ground and aircraft was supported by the tail post which fortunately had been hooked on. The loaders had to reload a loaded pallet into the forward position which restored the CG and brought the nose down and made unloading the remaining pallets from the rear easier as the deck angle had made moving these pallets uphill almost impossible.