It's not clear (from your linked first post) exactly how those rails are attached to the roof.. of course I could have missed something.
I know 2ea large wood screws on each corner into a 1/4" plywood underlayment holds a 135w panel just fine. I guess I'd recommend using more, but probably not 16.
Nice work all around by the way.
"If I'm wearing long pants, I'm too far north" - 2oldman