How far is the top netting going down the sides? I assumed that the top netting is going down the sides 4 feet to meet the 2' netting coming from the ground up. If it's only going to be a top cover, then your outside to outside run measurement can be 24'x24'.
If it's nylon or poly netting it's...
25'x25' minus 4' per side. For instance on the east/west sides the total will be 4' x 2 = 8', 25' minus 8' = 17'.
To make it easier to figure the numbers and to allow a bit extra on the netting the run should be 16'x16' outside measurement if I'm comprehending it correctly.