[Rader Sidetrack]

I think that such a large 'open' screened area would not be in the bees' best interest. Bees, when necessary, engage in thermoregulation of their brood area. Having free air movement through the bottom of that long Lang will likely make it harder for the bees to control the temperature.

Its not just heating the hive in cold weather, bees also set up their own "swamp cooler" system by hauling in water to evaporate and fanning to control air movement/evaporation when its hotter than what they want.

But you could have a screen floor that had a (removable) solid surface underneath it.

 

[Rader Sidetrack]

There are lots of beekeepers whose hives have a bottom board 'floor' using #8 screen.

The presence of the screen hasn't been reported as a problem. The controversy that arises is whether or not the screen should be closed off or not.