The sheet metal I put up 10? days ago has bowed under its own weight. I have added horizontal braces for reinforcements, and an extra vertical brace. It seems to be stiffer, and it seems also to follow a nice parabolic bend (or maybe a catenary?)
The smaller sheet metal had no reinforcement, and got its ass kicked. It was almost like a sail, catching the wind, blowing around, and making a racket. It is much stiffer now, and will hopefully hold up. I moved it from one window to the other, as I realized that the person on the fourth floor is throwing their garbage out the window onto the mirror. I discovered this because peanut shells fell on my head as I was making modifications to it while it was attached to the grate. I looked up to see more peanut shells sailing out of the fourth story window. Brooklyn... I will have to go ask them to not throw their trash out their window. I hope it goes well.