Scott used double nuts for a long time, especially for fastening the engine to the frame. One nut is the fastener, the second nut is a lock nut to avoid that vibration loosens the fastener. Works fine. Today’s solution would probably be a nyloc nut or Loctite 242.
On my bikes, some nuts were missing, and I made new in stainless steel from a 1″ hexagon bar. Took some time, but the result was nice.
Carl
