So, we had our coop delivered last Saturday.

I'm currently making plans for the run that we plan to create this spring, and I'm fairly certain we'll be going with welded wire for cost and ease of setup. 48ft. x 48ft. or something similar.
I have a bunch of questions, and I know there are lots of you who use ww for your runs, so I'm hoping you have some tips for me.
First off, the wire comes in several different heights, and I've been leaning toward the 5ft. one, since our chickens are all heavier breeds, not flighty. Will this be high enough? Does anyone use 4ft. or 6ft.?
The openings on all the wire I can readily find are 2" x 4". What do you do when your birds are small enough to fit through these openings or get stuck in them?
Do you cover your run with netting?
My mother has always used U-posts for her chicken fencing, but I see that T-posts are quite popular. Do you use one or the other?
What other tips do you have for putting the fence together? We still have a couple of months before we break ground, but I want to be able to keep an eye out for sales on the construction materials, etc.
Thank you in advance for any help you can give!