I have some questions about the number of down conductors required on a flat/gently sloping roof and a wall;

For a wall, say a mechanical yard wall that is 440' feet long and 1' wide, from one end to another that do not meet, how many down conductors are required? I say it is 6 since one is required at each end and 4 so that spacing does not exceed an average of 100'. Or is the correct answer 5?

Does a flat roof with a perimeter of 220 require 2 or 3 down conductors?

A structure 440' x 1' has a perimeter of 882' (440 + 440 + 1 + 1) and would require 9 down conductors. This example seems unlikely, if it's true I would consult your local inspecting agency for how they would rule it. However, since the term perimeter is not defined in chapter 3, the Merriam-Webster definition must be used.

According to M-W's definition, you need to imagine walking around the structure. This distance would be the perimeter. With this in mind, 5 down conductors would have an average spacing of 176.4' with 6 down conductors the spacing drops just slightly to 147', both exceed the maximum average spacing of 100' required in 4.9.10.2.

A flat or pitched roof with a perimeter of 220 feet would require a minimum 2 down conductors.

Reference to Standard