i got the outside rail for 5 elevation shows by showing up about an hour before doors. everyone was pretty much lining up to get in the heart, and it was very easy to get outside rail. vertigo shows, I had GA 3 times and all of them I got there mid afternoon, and could still get a spot 1 or 2 people back from the rail on the outside of the ellipse. once i got beeped in and was on the rail inside because so few had been let in. that was different though, since so many lining up really early didn't get beeped in and had to settle for outside rail. i would guess getting there at 3 in the afternoon i was still around the 400-500 people range.
maybe the stadiums will be very different, but my experience is that you don't have to stand in line all day to be very close. the earliest i have ever gotten there to get in line was on elevation at it was about 10am. I ended up front row center against the rail in front of bono. i was probably 50th in line, but i just got lucky i guess.