need tag feed plugin to get custom rss thumbnails

The description node in the feed from one my individual sites looks like this:

<description>
<![CDATA[
<img width="80" height="80" src="http://web.gcc.mass.edu/news/files/2011/11/moby-dick-80x80.jpg" class="attachment-sidebar-thumb wp-post-image" alt="moby-dick" title="moby-dick" />There are forty and odd vertebrae in all, which in the skeleton are not locked together. They mostly lie like the great knobbed blocks on a Gothic spire, forming solid courses of heavy masonry. The largest, a middle one, is in width something less than three feet, and in depth more than four. The smallest,...
]]>
</description>

You can see the feed here: http://web.gcc.mass.edu/news/feed/

When it's aggregated into the global tag feed, however, it looks like this:

<description>
<![CDATA[
<img class="size-full wp-image-871 aligncenter" title="moby-dick" src="http://web.gcc.mass.edu/news/files/2011/11/moby-dick.jpg" alt="" width="308" height="308" />There are forty and odd vertebrae in all, which in the skeleton are not locked together. They mostly lie like the great knobbed blocks on a Gothic spire, forming solid courses of heavy masonry. The largest, a middle one, is in width something less than three...
]]>
</description>

You can see the global feed here: http://web.gcc.mass.edu/wp-content/tag-feed.php?tag=home-feature

I need the global tag feed to match the individual site feeds!! Please help!!