code:

// ==UserScript==
// @name               shorter videos
// @namespace          [url]https://forums.somethingawful.com/[/url]
// @description        loving giant vertical recording
// @include            [url]https://forums.somethingawful.com/*[/url]
// @grant              GM_addStyle
// ==/UserScript==

GM_addStyle("video { max-height: 700px; max-width: 800px;} ");

window.addEventListener("load", function() {
    $("video").attr("controls", "controls");
}, false);