Is it possible to create column width presets in Gutenberg?

Gutenberg gives you some good choices out of the box but is it possible to add a custom preset? I understand I can change the columns manually but was hoping for a preset to make it easier on the client. My other thought was just manually change the 70/30 one to be more 80/20 in the CSS but again for lack of a better option. Any options as far as adding a preset?