marant, You will probably need to adjust your entrance size throughout the year to adapt to changing conditions.
When there is a good nectar flow on in the spring and early summer the bees seem to lose all interest in robbing and it's usually safe to have the entrance wide open. When the nectar flow dries up in the heat of the summer I choke my entrances back down to a smaller opening. It does create a bit of a traffic back up, but it's much easier for the guard bees to defend the entrance from robbers. When our Fall flow ramps up the entrances can be opened up again for a while. Then in late Fall the Yellow Jackets show up and it's once again time to reduce the entrance.
You will have different patterns in the south, just adjust to the changes as needed.