iOS app publishing update coming in April

A little late to the party, but for the iPhone X, has anyone implemented the viewport fit to “cover”, as well as declared safe areas using css for a bubble webpage? I’ve been able to implement the viewport fit to “cover”, as per iOS 11 Webview Viewport leaves 20 pixel white strip at top of page. But am having trouble declaring safe areas so content isn’t covered by the iPhone X notch. I presumed using css tools is the way to go to implement the env() function? Is this injection of css code even possible in bubble? Here’s the guide I’m following https://webkit.org/blog/7929/designing-websites-for-iphone-x/. @brentsum