Well updates here certainly dried up a bit, but I've still been making some slow progress.

The window dimensions weren't as advertised, so the design was revised to this three-concentrator box:

Which I've now built, but not before the windows got very dusty, as you can see.

Inside only one of the reflectors is usable, the drum that I was going to use for the other two turned out to be too rusty inside, so I need to cut open another one.

So the next step is to prepare two more reflectors with the chrome vinyl wrap and collector panel, then it's time to start on the plumbing.