[mikethedruid]

Are the NEC regs based on durability of construction or based on what kind of wire is the best conductor? 

It is the National Electrical Code, and is based on safety first, and functionality second. I recommend following it as closely as possible for fire insurance reasons. If you have an improperly installed outdoor antenna, and it is hit by lightning, resulting in a fire, you could have insurance problems. They are also very good from the standpoint of functionality. They also coincide with the FCC rules governing antennae, although those are primarily concerned with transmitting antennae. There are parts of the NEC that pertain to transmitting antennae but I have not included them since here we are concerned with receiving sets.