Option for setting MULTIPLE thumbnail sizes

I’ve been trying to set the thumbnail sizes for “Featured Post” and “Recent Post” with WordPress Multi-site and Site Wide Tags, but can only get add_filter( 'sitewide_tags_thumb_size'); to crop one thumbnail and not more than one.

Here is the code I’ve been messing around with:

// Set Thumbnail Size
add_image_size( '70px_70px', 70,70, true );
add_image_size( '550px_225px', 550,225, true );

function swt_550px_225px( $size ) {
	return '550px_225px';
}
add_filter( 'sitewide_tags_thumb_size', 'swt_550px_225px', 11);

function swt_70px_70px( $size ) {
	return '70px_70px';
}
add_filter( 'sitewide_tags_thumb_size', 'swt_70px_70px', 12);

Strangely, earlier today I was able to get both sizes to work by putting the filters inside the featured-post.php and recent-post.php include files, but later it stopped working and hasn’t worked since.

I have tried many variations of this code, but it always uses the highest priority.

Please help. I have been slamming my head against the wall for 2 days trying to get this relative simple feature to work.

http://wordpress.org/extend/plugins/wordpress-mu-sitewide-tags/

https://wordpress.org/plugins/wordpress-mu-sitewide-tags/