I ran into a lot of issues trying to figure out how to use the shared SSL and finally bought my own certificate for $40 and used SSLRedirect from Snowcovered.com. It works great for the site I used it on. On a different site I used a JavaScript I adapted from a John Mitchell post. It searches the incoming URL and adds www and https if necessary. Here's the link where I found it:

http://www.snapsis.com//tabid/560/forumid/12/postid/5068/view/topic/Post.aspx

And my code:

<script language="Javascript1.1" type="text/javascript">
    if(!(location.href.toLowerCase().indexOf('www.') > -1  )) 
             location.href = location.href.replace('http://avalon','http://www.avalon');
</script>
<script language="Javascript1.1" type="text/javascript">
    if(location.protocol.toLowerCase() =='http:' &&
       ( location.href.toLowerCase().indexOf('login') > -1 ||
         location.href.toLowerCase().indexOf('mycart') > -1 ||
         location.href.toLowerCase().indexOf('180') > -1 ||
         location.href.toLowerCase().indexOf('register') > -1||
         location.href.toLowerCase().indexOf('orders') > -1  )) 
             location.href = location.href.replace('http:','https:');

    if(location.protocol.toLowerCase() =='https:' &&
         location.href.toLowerCase().indexOf('login') == -1 &&
         location.href.toLowerCase().indexOf('mycart') == -1 &&
         location.href.toLowerCase().indexOf('180') == -1 &&
         location.href.toLowerCase().indexOf('register') == -1 &&
         location.href.toLowerCase().indexOf('orders') == -1)
             location.href = location.href.replace('https:','http:');
</script>

Hope that helps at least a little.