I'm brand new to WPMUDEV and I'm installing & configuring

Hi, I'm brand new to WPMUDEV and I'm installing & configuring my first plugin to be used on a public site.

Is there a way to instruct *via opengraph* the plugin to include a specific image size of all the available thumbnails for a particular image?

Let's say that I have a post with a featured image that it is used on my template as a very large image but I have a thumbnail editor and have a manually cropped thumb on a smaller size showing the part of the image that I want, so I would like that when a visitor shares this on FB, the image chosen by the plugin is NOT the featured per se, but the featured media file on a specified size.

Does this sounds reasonable? - I know that there is no way currently to set this up via the admin dashboard, but I'm willing to modify the plugin script (I'm a PHP programmer) in order to send the image I want.

Any clues?

Thank you in advance.