Hi Ken!
Switched from Madison to Norris this last summer, on August 6th (Tuesday).
We broke camp at Madison by 6:45, and were setup by 7:30 at Norris.
THEN we had breakfast. That was the correct choice, as a half a hour later there were quite a few more folks circling for spots. I would try to get there by 7. Would you get one later, probably, as more were packing up later on. You will just spend more time looking.
Was my first time at Norris, since I generally hop to the opposite side of the park after Madison. I would go back. Bit more rustic than Madison, which is my preference.
The entire week's visit was impromptu, rain in Colorado forced us northward. Was able to call and get two nights at Madison two days out, then hopped the rest of the stay. Had always avoided July/August before because of crowds, but really was quite manageable. Just do crowded activites early, and hike the crowded times. Very pleasantly surprised.