>All the observation hives I've seen have the entrance on the bottom. Does anyone foresee any problems with it on top?

It eliminates one of the problems I've had with Observation hives when too many bees die and plug up the exit. Sometimes in winter. Sometimes when the population peaks. Sometimes when the big hives want to rob them. Of course it might be an advantage in the robbing scenario.

In spite of the entrance being on the bottom on mine, I always see bees hauling dead bees to the top of the hive. I don't know why and they don't accumulate there, so I assume they eventually figure out that's not the place to take them.