I've read a number of threads about swarming, swarm traps, etc. And I did not want to bury this in some worn out topic. So I hope this might help someone.
One of the best books on the topic of swarms is a small book entitled "swarming" from ROOT publications. Item #56 (1-800-289-7668)
It covers studies in swarm trap comparisions, feral colony preference, why hives swarm, and a host of other topics all related to swarming, control, and prevention. It is a collection of articles written in Bee Culture from people to include Roger Morse, Bonney, and others.
It is about swarming, but it will enlighten you in the facts of swarms favoring small cavities, the fact that most feral colonies requeen every year, etc.
Well worth the $5