Well, that took a while - I can't recommend the shops for the 28 mm tubing system I linked in a previous post.
However, the prototype is now in action. It is not really meant to be mounted this high, but the ledge below the panel predetermines that in this case. I will set up the panel properly in another location soon.
Things that I would change in the next iteration:

• The equipment feet on the horizontal tube that I use to clamp it into the scuncheon should be more robust, maybe from massive plastic or turned aluminium parts rather than sheet metal. I will try 3d-printed parts soon.
• The tube construction besides the horizontal bar in the scuncheon is robust, but fiddly to assemble. I am already thinking of other options, probably of bent sheet metal.