Script EPUB export not including JS/CSS with epubFixedLayoutExportPreferences

Hi

OSX 10.9.4; Indesign CC 2014.1 10.1.0.71

I'm trying to include JS & CSS files with my Fixed_Layout EPUB using the following code:

var ip = app.activeDocument.filePath.toString();

var doc = app.activeDocument;

with(doc.epubFixedLayoutExportPreferences) 

{

externalStyleSheets = [ip+"/Es.css"];

javascripts = [ip+"/Es.js"]

}

doc.exportFile(ExportFormat.FIXED_LAYOUT_EPUB, File(ip+"/Build/"+fileName+"/EPUB/"+fileName+".epub"),false);

The EPUB builds without errors but neither CSS or JS file is included within the EPUB.

Any ideas?

Cheers