According to Thomas Seeley, who has researched the topic and written Honeybee Democracy, they prefer a 40L cavity (about the same as a 10 frame deep) with a 1.25" entrance. I use 5 frame nucs with 3/4" entrances and have success. The only attractant I use is LGO which seems to make up for the shortcomings of my traps. Sounds like a Warre hive that equals two 5 frame nucs is just about the right size. Use LGO and size really doesn't matter. Happy trapping.