"missing cover" in docbook epub converted to Amazon kindle .mobi file

I'm using an epub generated from a Docbook transformed via ANT in Oxygen to create a .mobi file for the Amazon Kindle (using Kindle Previewer). It keeps giving me a "missing cover" warning, which is displayed over the cover image. The Kindle Previewer documentation says that the cover should be included this way: Define covers in the OPF file using the following tags:<metadata>...<meta name="cover" content="my-cover-image" >...</metadata> ... <manifest>...<item href="" id="my-cover-image" media-type="image/jpeg" >...</manifest>But I'm having trouble figuring out how to insert that into the DocBook file, or into the ePub using Oxygen's Archive Browser. I think I would probably have to insert that file in more than just the manifest folder. Also would it conflict with the "cover.jpg" file that's already in the ePub?Any suggestions? thanks! DC Denison