I could only make it work by changing my windows screen resolution to 1920x1080. Made a little BAT to change resolutions (using a command line utility that changes screen resolution), but it would be nicer if GOG provides a cleaner solution to this. Perhaps there is a way to force the program to start in a determined resolution?

There are several games having problems with running in fullscreen on very high desktop resolutions. Programmers simply didn't tested them under these conditions as ultra high resolutions were very rare some years ago (especially on the y-axis).
Maybe it's possible to provide a hack in this case, but as these resolutions are still uncommon, I doubt we'll see someone putting work into this anytime soon. Teach me wrong GOG! ;-)

You should create a support request to let them know.