I think the viewport meta tag is potentially a side-track. I used the Google-recommended <meta name=viewport content="width=device-width, initial-scale=1"> on pages of a website and got an "Awesome your website is mobile friendly" from Google BUT only a 1/3rd of the page width was displayed on an iPhone 5C and pinch & zoom was disabled. Quite unacceptable and unusable for the viewer. I get a good display with <meta name=viewport content="width=device-width, width=660, initial-scale=1"> but Google doesn't like that at all...