I've been reading about stopovers and am trying to wrap my head around it.

For context I have 125k AA and 70k UR. I'm hoping to go from Boston to Shanghai, then Japan, then back to Boston in April 2014. Is there any way I could make Shanghai a stopover or is that not at all possible assuming the flight path would go through Japan first? I only have barely enough miles to cover myself and a friend economy, so I'm trying to see where I can save and hopefully boost us up to at least business class. Thanks