Custom Feed URLs

As Krzysiek says its hard to give a good answer without knowing how your doing your feeds. But assuming that you’ve extended the default wordpress feeds so your feed could be accessed by going to index.php?feed=userdefinedname, then this rewrite rule should do the job for you.

add_rewrite_rule(
    '^feed/(.+)/(.+)?/?$',
    'index.php?feed=$matches[1]&category_name=$matches[2]',
    'top'
); // /feed/userdefinedname/testcategory