[RE-wrenches] Using Metal Roof as conductor

[Jason Szumlanski]

I am installing a PV array at about 400Vdc on a metal roof. The inverter
is located a very long way from the array. I am contemplating just
running a positive conductor for most of the run. I was thinking about
connecting the negative PV conductor to a lug solidly bonded to the
metal roof material. Then at the bottom of the roof, near the eave, I
would attach another lug and continue with a negative PV conductor. At
junctions of the roof material, I would drive a self-tapping stainless
steel screw for continuity (with sealant, of course). This would save
lots of copper. And since the negative conductor is bonded to the module
frame by way of the metal roof, the negative PV conductor would also
serve as the ground wire.

What do you think? Would this pass inspection? What NEC sections would
apply?

Thank you for your time,

Solar Guru

P.S. April Fools