The Size Of LMB

How big is the LMB should be in a BH ????
Below is the spec !!!!
1) The LMB is depend on the BH size.
If your BH is larger enough, then we can open the LMB more bigger. Why ? Because there will still have more space on the dark side and the bright side.

2) What is the design of the BH ? Open Roof ? Window type ?
This is due to the wing( air ) effect and due to the " Pencuri "

3) Where is your BH located at ?
Are this BH is stand alone or shop lot ?

From the pictured i attach, the LMB size is 5 feet X 7 Feet !!!! This BH is a open roof type and it is stand alone BH that is located in the middle of the padi Field. The external roving area is 20 feet X 40 Feet and have a small pool at this area. The internal roving area is also 20 feet X 40 feet.
In 3 year time, this BH already have 3000 nest. Very good result !!!!!