I was asked; How I attached the winter front to the grill on my previous post; so thought I'd post it here in case anyone else is interested.
I made backing strips out of 1/8" x 1" aluminum flat stock so it was flexible but stiff enough for support. I drilled and tapped for 10-28 screws.
The screws are 1 1/2" stainless allen heads with flat washers tightened just enough to keep the thing in place and jam nuts on back to keep them from falling out.
Also I saved the templates as .pdf files so they can printed if I need them again later if anyone is interested in them. They are just a rough template though might need a little tweeking.
Inside view: