I'm going to disagree with everyone that said ACM is not strong enough. by itself. I installed a double sided
sign where the upper part was 2 sheets to make an 8' x 8' panel then a 2 foot gap with a 5' x 14' bottom panel. I installed wooden stringers onto steel wide flange beams 30 feet tall. I fastened the panels with good sized pan head screws around the perimeter and also had a few cross wise stringers. The
sign took a direct hit from an F1 to F2 tornado which ripped the roof off their steel building and twisted the steel poles a bit, but all the panels stayed intact.