I personally put a piece of newspaper between the two deeps and let nature take its place. If the two queens fight they fight, but I never had them swarm or leave after I put them together. They eat thru the newspaper and their scent and stuff mixes and they are all best of friends after 2-3 days. Never had one of the queens leave the hive with the bees after or had a bunch of dead bees before so something works somehow. After a week if they have any empty frames between the two deeps I move them to the top and fill the bottom full first and take out any uneaten remains of the newspaper. It is neat how it works. :-D