Hi James,
There are threads/posts further back if you sift through them. Some by ukroosterman, devonflighter and others.
Standard size flight pen for 1 bird is about 4'x4' for pair's about 4'x8' ish.
I have permanent pens 2mx4m for pairs. Others folk may differ. Barrels and tethers are great for single bird's. I have made them with perch on top, perch inside, wired up the bottom and made it so a door can go on at night. Easily moveable for fresh grass.
Hope this helps :-)
Atb