When not using the full page width option, the colums on a Zen Foundation page are all fixed width, and I can't find a setting in the brand designer that changes that. The effect is that when the user makes the page wider, the content stays the same.
What I'd like is to have the center (main) page panel always behave as it does wih the full width option -- it fills up the available space (width apparently set to 100%).
FWIW, I've tried (using the Chrome developer tools) explicitly setting "width:100%" on the center column, and it doesn't do what I'd expect -- the width of the column is still fixed, though a bit wider than the default.
I've also tried removing the side panels from the master page. In that case, the center (now only) column is still fixed-width.
Finally, I tried setting width to 100% explicitly on the main zen section on one of the pages. Again, the setting seems to be mostly ignored -- the section is still fixed-width.