Ok so a few bits to post here - This build was quick and pretty easy, longest part was the design and math
Definitely worth a go!!
I'll start with the frame, See attached! I've used the same materials as mentioned by John.
6060 T5 3mm thick.
Most of the frame is 25mm OD and 32mm OD joiners.
I purchased the cheap $208 AUD bender.
It does a nice job- clean up the edges with a file and add some vaseline around the fulcrum
Ledge frame is 930mm X 2060mm OD
I managed to get the side bars to collapse and fit inside the horse shoe bends (930 - 50 = 880mm) .. see all math on attached.
However, once I added the Shock cord around the tube this become less relevant.. hahah

My first test was BCC (Big Canopy Campout) weekend. I slept comfortably up a Mountain Ash, 70m off the forest floor. However, I didn't have time to make a fly so waking up to rain was an experience. To my luck it was light rain and the bivie bag did the job.
Bed base design to come..