I have successfully used the explain parameter in my query to return _shard and _node for each hit (which is exactly what I needed). I actually don't need all of the additional score computation detail (which is most likely very performance-expensive and it returns a very large response body).
I am probably overlooking it in the docs, but is there a query parameter that I can specify to add the _shard and _node for each hit without requesting an explanation with all of the extraneous detail?