OK here is what I added to the header template, if anyone’s interested.
<?php
if (is_category()) {
$fullrss = get_category_rss_link(0,intval( get_query_var('cat')));
} else {
$full_rss = get_bloginfo_rss('rss2_url');
};
$rss2_url = $fullrss;
$rss_url = $fullrss."rss/";
$atom_url = $fullrss."atom/";
?>
<link rel="alternate" type="application/rss+xml" title="RSS 2.0" href="<?php echo $rss2_url; ?>" />
<link rel="alternate" type="text/xml" title="RSS .92" href="<?php echo $rss_url; ?>" />
<link rel="alternate" type="application/atom+xml" title="Atom 0.3" href="<?php echo $atom_url; ?>" />