How to define embeded page preview preferences

Hi,

    In the InDesign C5 client version, there is a Preference under "Files Administration" in the preview settings called "Pages". Where is this setting in the InDesign Server DOM? How should I configure the settings for the embeded previews with InDesign Server? What I'm using at this moment is what follows, but doesn't seem to be enough to embed the page previews in the InDesign Document.

    with (app.generalPreferences) {

        includePreview = true;

        previewSize    = PreviewSizeOptions.MEDIUM;

    }

Thanks in advance

Aleix