I am having the same problem, I would like to show the full post, but the post is being truncated, and not at the <more> tag.
I am trying to do this for a page of posts from a specific tag
https://stonebergdesign.com/tag/planet-drupal
I have changed the setting referred to above, but with no love.
I am using WP 2.5
In my header I put :
<link rel="alternate" type="application/rss+xml" title="<?php bloginfo('name'); ?> RSS Feed" href="<?php bloginfo('rss2_url'); ?>" />
here is the feed link:
https://stonebergdesign.com/tag/planet-drupal/feed
which you will see is truncated.
Is this something I can adjust in the feed-rss2.php file?
Thanks