Rodney,
You will NOT need any spacer between the two hive bodies.  Do NOT use 2
sheets of
newspaper, one is plenty, and two sheets just makes too much "garbage" for
the bees to remove from the hive.

You are correct when you say "most people just let the queens fight", and
hope the youngest one wins.  That is OK, if the queens are of equal quality.
However, if one queen is definitely superior to the other,  it behooves you
to kill the lousy queen
before you try and combine the two colonies; and his almost guarantees you
the better queen will become queen of both colonies.

While not extremely important, it is thought best to put the hive containing
the
good queen on TOP of the hive containing the bad queen.

Hoping I have helped.

George Imirie