Two and a half years ago in April, three of us in three boats continued past Diamond on our trip. We were somewhere around 10000-12000cfs if I remember right. As I recall looking at the notes I made on my map, there wasn't much available past 240 or so. We ended up staying one night on a sandbar river right at about 259.5 directly below the heliport that is on river left. It was fun sitting there watching the helicopter tourists watching us from the canyon rim. The second night we found what turned out to be a nice ledge camp at about 277.6 right past the left bend in the river.
Other notes I took as we floated by:
260.7 Left - Lower Quatermaster was still there, but very steep banks to get up to it
261.7 Left - decent looking possible small camp site
264.9 Right - sandbar that could be a camp site
271.0 Right - decent looking possible camp site
274.0 Left - nice looking sand bar
279.0 Right - Very large nice campsite. Big enough for 30-40 people. When we passed, there were three large groups there packing up.
Hope that helps.