I fiddled with your downloadable examples a little and changed in the narrow css file #page-wrap {width: 548;} in #page-wrap {max-width:548;} to make the text wrap on smaller screens.
Now I want to add an image to the wide and the middle layouts and a smaller version of the same image to the narrow layout.
I just want to use good old css to keep things simple and stay out of trouble, but I can’t get it working though )-;
Probably I’m overlooking the obvious.
Any help is really appreciated.