Another question I thought of....

Should the arch run east to west or north to south?

I prefer to run them east to west. I have run short hoops north to south and the south side plants got a little stunted. If you go east/west, not only do all the plants get sun, but you can grow plants underneath the hoop and they get sun too.

Cattle and hog panels are sold at 16 feet. The other measurements can be your choice. You don't even need T posts, I made a hog panel trellis by burying the ends in the ground, or you could butt them to stakes. You should also have wire or twine to tie them to the stakes or posts.

The NORTH side plants got a little stunted.

Thanks happyday. After your post I had to think about this a little more. For most of our summer months sun up is around 5:30 and the sun crosses the sky north of us. Because of this I would think the arch should run north to south. That way one side would get morning sun and the other would get afternoon sun. If I run it east to west the south side will not get any direct sun. I plant trees east to west but I think this should run north to south.

I have a bad back and neck and I'm going to have to build this alone. Knowing at what distance to place the ends of the cattle panel so that the peak of the arch would be 6' 3" to 6' 8" would be helpful if anybody knows. For me it sure would be a pain to have to hold down both ends and measure the center at the same time. I can think of several ways to do it if I have to. However it would be faster and possibly save me a lot of physical pain if I knew the distance to start with.

Which hemisphere do you live in? Are you saying that your sun rises in the north and sets in the south?

Same hemisphere but a lot further south than you. I live in Arizona. Right now the sun is south of us. However during the summer months the sun rises east north east and sets west north west. It crosses the sky north of us.