Need to make the hole big enough for two drones to exit at the same time. Anywhere from 1/2" to 3/4" works really good, the bees do not come back to the hole in the end of the cone, they return as close as possible to the entrance hole that they have oriented to. When you place your bait hive get the entrance as close as possible to the parent hive entrance, not the end of the cone. Hardware cloth works better than screen wire (it will work though) because the holes are bigger and makes it more confusing to the bees or harder to orient to the end of the cone. The finer the screen, it starts to look more like a pipe that they can see the end or entrance to.
I think you are confusing a trap out cone made of number eight hardware cloth with the Hogan style of trap out box.
Post up a few pics and lets see what you have going on.