Possible to insert bluga module functions into Contemplate

I'm using the bluga module to create thumbnails of URLs using this function in my php template files for a CCK content type:

bluga_webthumb($url, 'medium2')

This inserts the thumbnail created from the bluga service into the node. The thumbnail is served from my files/ directory.

I'd like to be able to affect my RSS output so that I can include those thumbnails in my RSS feeds. I've tried this in my contemplate form for RSS output:

print bluga_webthumb($node->field_url[0]['value'], 'medium2');

But I'm not getting anything back. Any suggestions on how to make this work? Thanks very much.