Elliot and I tested the polished panels weekend before last.
They functioned, but our calorimetric tests were a miserable failure. We conclude that we can focus the rays but it is very hard to get them into the target. We can probably toast bread well, because it is a nice, flat, target. However, attempting to heat our jar of water was very ineffective.
However, we are not giving up. Rather, we are now going to investigate using a large Fresnel lens, which Elliot happens to have.