Cannot set width for fluid theme.

Steps to reproduce:

1. Activate the "Fusion Starter Lite" theme (though this should apply to all fusion derived themes).
2. Configure the theme fluid so that it is fluid at 85% of the window width (Configure > Theme-specific settings > Fusion theme settings > General Settings > Layout)
3. You will note that even above the minimum row width (780px) the content takes up 100% of the page width

Solution:
A look at the CSS reveals why.

/* theme setting: set fluid grid width on top-level full-width elements */
.fluid-100 .full-width .grid12-12 {width: 100%;}
.fluid-95 .full-width .grid12-12 {width: 95%;}
.fluid-90 .full-width .grid12-12 {width: 90%;}
.fluid-85 .full-width .grid12-12 {width: 85%;}

The .full-width class needs to be applied to the .page <div>.