I'm now sorry that I brought this subject up. After working in the aircraft industry I guess I tend to err on the side of caution. At the time inspectors demanded that between two to four threads were visible past the end of a nut, but we were dealing with vibration issues which hopefully you won't be. Everything, generally, was either a locking type nut or castle nut. The castle nuts were for safety wiring purposes and most often found around the engines and they were also used on any exterior lighting.
This could be where Jerry is coming from since he spent most of his time in aircraft and running diggers and floppers.