500W Panels - back mounted - 4 bolts only?

[eXodus]

Got the mounts figured out with 2x M8 screws.

Whatever aluminum alloy they made the panel-frame from - is pretty sturdy, it was much more difficult to drill then the aluminum brackets.
Might not as big of a concern as I thought initially.

Well, now it's done. 15 minutes extra per panel. Additional $3 in fasteners. Piece of mind

What bolts/system are you going to use to bolt the 550w down?

see pictures.