How can I set 'styles' for li elements in CKEditor 4?

Basically, I'm wanting to be able to create a style that will allow me to turn a regular unordered list into a two-column list. Something like this:

CKEDITOR.stylesSet.add( 'default', [
    {
        name: 'Two-column List',
        element: 'ul',
        styles: {
            element: 'li',
            styles: {
                'display': 'inline-block',
                'width': '50%',
                'float': 'left'
            }
        }
    },
}

But it apparently doesn't work this way. Does anyone know of a good way to style child elements via the CKEditor styling?

Thanks!