In particular, I'd like to add
<meta name="viewport" content="user-scalable=no, width=device-width, maximum-scale=1, initial-scale=1, minimum-scale=1">
and when I insert it into the head from JS, I'm still able to scroll horizontally on mobile browsers, so I'm guessing it needs to be in the head a load time.
<head>
block? – Resolutive