Looks like scaling to correct aspect ratio ist lost when going fullscreen? Or at least I am not able to get it right...

aspect=true (also tried aspect=yes)

Does not matter if I use overlay or overlay2. As soon as I go fullscreen the correct 4:3 aspect ratio is lost. In windowed mode everything looks fine.

Also I am not able to set the keyboard to german layout correctly. I thought keyb GR 437 inside DOSbox would do it, but still Y/Z are mixed up.