In my TBH's, the worker bee cell size is 5.3 mm. Both were begun with
sounthern queens and bees from my standard hives.
I have had bee trees (feral hives) close to my house and under
observation for over 8 years. Not one such hive has ever survived the
winter. Unless I am able to seal off the dead hive in a bee tree, it is
the first place to be taken over by a Spring swarm some of which (but
not all) come from my own hives.
Burns