Hi Matt,
Our current resizer doesn’t work like that, unfortunately.
However, we’re ditching the current resizer in the next version, so your add_image_size
code is the way to go.
To use it, simply remove your width/height values in the Customizer, and do this:
add_filter( 'generate_page_header_default_size', function( $size ) {
return 'figurethumb';
} );
This is how the resizer will work in the next version, except you’ll be able to choose figurethumb
as the image size in the Customizer.
Let me know if you need more info 🙂