Remove header from Android Web View (Android SmartWebView)

I'm using mgks Android WebView app project, which works great, but I have to make one adjustment. I would like to remove the from the website once rendered inside app.

I've tried basically all code from the replies in similar questions here, but none of them seems to be working. Does anyone use this repo and have done it or knows how removing header would be possible. If not embedding a new CSS file from assets is also a welcome option, I will overwrite it there.

I've been adding all the hacks to this part:

public void onPageFinished(WebView view, String url) {

            print_page(view,view.getTitle(),false);

            super.onPageFinished(view, url);
        }

Thanks for any useful ideas.