Anyone tell how to place the beating heart mechanism inside the body of the doll? I would like to start adding them to my dolls, but am not sure about the battery issue. What kind of body must be used and how is it inserted....I would think it would take a special body with some way to access the battery when it needs to be changed so the doll doesn't need to be reassembled? Or perhaps behind a body armature (frontal) somehow? Can anyone tell me the BEST way to do this? Thanks a million.....