I have used this in my PCV frame blind since way back 1993 or so. Mine is alum tubes I covered with pipe insulation to prevent noise if I were to hit it.
https://www.google.com/url?sa=i&rct=...20529829351653
For my perment box blinds I use two others and a couple of bag chairs.
I like back support now adays. when I was just a pup I carryed a home made sort of directors chair short and no back. when I found a place I wanted to sit I just unfolded it.
. Al