User stylesheets in NetSurf?

Does anyone know whether it’s possible to set up a user stylesheet¹ in NetSurf? I don’t see anything in the UI for it, but there are a couple of CSS files in the app directory so I wonder whether I can edit one, or add a new one with a specific name.

Any ideas?

¹ For those unfamiliar with these, it’s a way to override the CSS provided by a site with your own. Most browsers have an option buried somewhere in the settings to choose your own style sheet. You can use this to, for example, make the default page body black and the text colour white. Or, in this particular case, I’d use it to “fix” a couple of sites that don’t have NetSurf-compatible CSS.

In Choices.WWW.NetSurf create file “User”, typed CSS.

As simple as that! Thanks :)