Hi Greg. Yes, the back comes in for a bit of a pasting. I was horrified at the prices for a special astro chair, so I did this:::::
I got a small step ladder from Bunnings (2 steps plus top one). Then
I cut out a piece of 1 inch plywood (you could use something similar) and attached it to the second step with a waste piece of 6 mm bar bent like an S shape and fitting into a hole in the ply. I then add a cushion and another piece of wood (actually a wooden chopping board)
, and for those real high occasions, I use a folded up children's life jacket to get even more height. Cumbersome? Not a bit of it. Very comfy and stable, and the whole thing comes apart for when you have to change a light bulb in the ceiling using the step ladder in "Original" mode
