As you see, they will settle 35 feet up. That colony did, so 30 should be fine.
Things to remember......
They work best 100 to 1000 feet away from mother colony.
10 feet away may be passed by.
They should have the entrance facing south to east.
An empty 10 frame hive weighs approx. 35 lb. A large swarm can gather 60 lb. of honey in a week during a good flow. That puts the box, bottom, lid, and contents weighing over a hundred lbs. a week or a little more after they move in.
So a guy calls me and says..." Im the one who called John and asked for help but he declined, but I know you are gonna catch the swarm with your trap. I want the bees since it was my idea".......So I called him back and said " I will go take the trap down, and let you try. My intent by putting the trap up there was to get the BEES!" Lucky for me,..... you have to be able to climb to get to it...
Long story short, he calls back and says nevermind, leave the trap there and good luck. It amazes me sometimes how everyone wants in on the action when the work has been done!!! DOH!