I have a 1968 pa-28-180. Im a little confused as when to turn the Master switch off. Before I kill the engine or after? Ive seen it both ways on so many checklist that I'm not sure which way is right and why. I do remember when I was in flight school flying a Cessna 172p that the checklist calls to shut the Master off before shutting down the engine, but I'm not flying a Cessna. Any help would be great. Thanks