Just a thought Nug... I've learned from this forum a trick or two about helping a swarm stay put.
You can put a frame of brood from another hive into the swarm hive, that can serve as an anchor to keep them in the box.
Or, you can put a queen excluder between the bottom board and the hive box for about 4-5 days. If the queen can't get out then the bees won't leave.
You prob already know this, just adding my two cents
