Thanks for the help, netseeker. I tried what you suggested (using "preface" instead of "text", and <a id="preface"/>, it validates correctly in Flight Crew! But unfortunately after converting to Mobi with Calibre it still doesn't open on cover in KindlePreviewer. :/
Not sure what I'm doing wrong. Maybe I'm placing the <a id> at a wrong place? This is on my first file, the one with the cover on: <div><a name="preface"/><img alt="cover" class="sgc-1" src="../Images/cover.jpg" /></div>