This isn't really a question, but I just wanted to mention to the devs that when I downloaded the install files, the second install file was incorrectly named (and also in the wrong format), causing the setup to fail to find the right file. I downloaded the files using the GOG Air downloader, and the second install file was in a "GOG downloader" format or something along those lines. Upon realising the problem, I renamed the file (and format) to that which the set-up wanted, which solved the error, and the game seems to have installed just fine.

Was the name really wrong or was it just missing the .bin extension ?

In any case, that sometimes happen when you use the downloader, on ocasion files will arrive at our end without the extension. If you check the downloads with the browser you'll notice the files are all correctly named and all have their proper extension.

It had both the wrong name and the wrong extension - it was still apparent that it was the second install file, but the name had a different format to the other two files.