Featured image size in ADMIN panel?

I want to be entirely clear about this, what I’d like to do is change the size of the featured image thumbnail on the ADMIN panel, not on the front end.

I’m building a WP-admin theme, and I need to make the featured image larger on the back end.

It seems, featured images in the edit-post screen always spit out at 266x148px, ideally I’d like them to be actual size.
I’ve searched around and can’t find any hooks or functions that’d let me do this, but if anyone knows how, it’s the people on here.

You can filter 'admin_post_thumbnail_html' and replace the img element with a new one in the size you need.

Everything else will get messy and might lead to side effects.

• Filtering image_downsize while watching for a size of 266×266 might affect images that are not meant to be shown in the metabox.
• Changing the size for post-thumbnail temporary is not easy, because there are no safe points to start and end such a filter.