Two years ago I made six 40L swarm traps that worked well. Living in a rainforest, the environment has not been kind to the plywood and all have separation issues now, despite a good painting when they were built.
This year, I've already caught 2 swarms in the last month using the 8-frame hives that I use in by bee yard. Having read The Honeybee Democracy over the winter, I approached my setup a bit more methodically this year. I put in only 4 frames the 8-frame body: 2 drawn out frames of comb and 2 frames with just foundation; I left the remaining space empty so the scouts feel like there's room for expansion. A spritz of SC to the underside of the inner cover and another spritz at the entrance and that's it. 100% success so far this month (2 of 2). Going to place another two out this week after all the rain subsides.
Aside from not having to make a special trap box like I did prior, I don't have to transfer them as they're moving themselves right into their permanent hive from the get-go--just relocate! I place all of my traps at 3-4' from the ground--no concern for the bees it seems, and it's easy for me to check, service and move.