valid point on the 4 lanes into 2, and I did think about that as well.
I came into some insane thought of bees liking to build downward, since thats what they do in nature. plus with a bottom entrance, it is less travel room from the entrance to put pollen/etc, and it is also less hot, I would figure, since heat rises. less heat means less work ventilating, yet since the heat gathers at the top of the hive, they can move up if they wish to get warmer by chance. Less work means bees do not exhaust themselves out and die younger (which is why bees live longer through winter than summer I believe.)
does it make it harder to do a inspection? yes and no...I sugar dust anyways for mite control, and do both brood chambers. I also clean out my bottom board, and only switch to a screened board much later in the season....never known a natural hive to have a screened bottom in it frankly....
anyways that is my thought process.