I have buckets full of 8 inch triangles already painted for back corner support and generally don't even install them until a panel becomes weak or needs a repair.
Nails are still a definite no no. As the panel wiggles around these nails can work their way out and become things for patrons to get cut on as they go by. With screws you can take off a whole piece of lumber and replace it. Some things being not totally square are okay but then you discover some helper did something totally irregular and have to redo it. With screws you can totally redo it. Sometimes you don't find wonky things until you are setting up. Trying to stick this next to that. Even doing everything yourself you become tired and have to deal with #2 and #3 lumber that you think you have bent straight and then screwed in. Again you don't find it until you actually try to set up.
Another fabulous post from the U.S.Department of Wild Imaginings, now in spectaclar stereo, sponsored by the Adhesives and Sealants Council, suggesting ways to stick things together since the 1800s. Not fabulous in a gay way. Your results may vary. Illinois residents add 8% sales tax. These posts have been made by professional post makers, do not try this type of posting on your own without extensive training, lovely assistants and a trusty clown horn.