To prevent the netting from sagging, many people will use coated cables or rope attached to a center pole going out to a corner post of the pen. My current pen does not have cables or rope to help hold up the netting, and I can see why it is better to have that extra support. After a few years now my netting is low in some areas and fine in others. Also consider if the pen is right under a tree. You will get so annoyed removing sticks off of the netting. The oak tree next to my pen is always shedding sticks and the corner of the pen is covered in sticks and I can clean it one day only to have more in the netting the next day. I love the tree so it isn't like I would just cut down the tree.
Yes they will. I don't know if my raccoon issue was from them chewing through or if the post had already rubbed a hole in the netting for them to enter through, but they came in and killed a fully grown peacock. In total I have lost 3 peafowl to raccoons since I have been raising peafowl. I still think that netting is good even if raccoons can chew through it, so that is why I think my best option is surrounding the pen with hot wire.
The above photo shows the use of cable or rope to help hold up the netting.
I second the part about getting knotted netting instead of knitted. I think if knotted netting rips it isn't as big a deal like it would be if knitted netting rips. Some people do use knitted netting and say it lasts long too, but far more people recommend going with the knotted netting and the large scale ring neck pheasant breeders use knotted netting and with the massive netted flight pens they build, they ought to know what they are talking about as far as netting goes.
Dylansmom did you concrete the wooden posts into the ground?