If using 1 inch, make sure you have the bracket anchored well, and if on a pole, make sure it's in the ground really well. That's a lot of weight over time and we have all seen our fair share of drooping, hanging
signs over the years. If I were going to make a
sign like that, I would fab up the hangers that would clamp the panel on both sides too so it didn't rip out the holes the first storm that came along.