At Area 51 Walt Ray had the room next to me. One day he said that he could not get his head against the headrest on the ejection seat with our oversized parachute. My comment was that this was a non problem, as Ken Collins found out early on when he bailed out.
On the day Walt was killed I had an early flight, the longest by a project pilot at that time, three air refuelings and all over country. Walt had the later mission which was shorter. When I got to the aircraft all suited up I noticed a balsa wood spacer glued on the headrest about two inches thick. I asked about it and was assured it was OK. I assumed it had been tested. It had not.
When Walt ejected the butt snapper fired and as it tried to separate him from the seat the survival kit pushed the parachute up and it wedged against the balsa wood block. He was locked into the seat with no way out.
A day or two later I knew the seat was going to be hung in a hangar and tested to see if the seat would separate when the “butt snapper” fired. I arrived just after they quit. It failed seven times in a row. This unauthorized, untested mod killed Walt. It was the failure of a system that allowed untested modifications to be made with no supervisory oversight.