Hi Tim,
I remember reading somewhere that camping is permitted, provided you are more than one hour’s hike from the tourist lookouts.
If you walk slowly, the Prom area etc is an hour from the Z-Bend lookout… I’ve camped there several times. If the water is low (and there’s no flash floods…) there’s a nice sandy beach to camp on. Otherwise up higher under the overhang area.
Just camp out of sight of the lookout, take all your rubbish out, don’t make a mess, and don’t crap near the water, rock or hiking path. Also be aware of fire restrictions – probably best not to have any fires at all (apart from a jetboil etc) if you don’t want to attract attention.
And travel light – carrying climbing and camping gear, food and water in isn’t too bad, but having to carry most of it out is the hard part!
Have fun!