Re: FMC
Hi Wayne,
FMC can be installed at any length. When it is, it needs to be secured and supported within 12" of each termination AND every 4 1/2 feet.
If used to wire lighting in a drop ceiling, the FMC may not be secured to the same support wires that support the ceiling. They need their own support wires!
When the length does not exceed 6' from a junction box to a lighting fixture only, no securing is required.
When run from fixture to fixture, regardless of length, it is required to be secured.