[RE-wrenches] Metal roof/self taping screws

[Jay]

What do people recommend for a metal roof ( with flat sections, not corrugated)on 3/16” thick x 2” wide C channel for attaching L feet

Self taping fasteners would be the easiest. Doing a nut and bolt would be possible but quite time consuming. 
A machine self taping bolt and then adding a nut would be a lot easier than nut and bolt. 

But that is my question. Is a self taping screw enough or does it need to be bolted?  

Jay
Peltz power