@iceberg, if you need something quick and dirty, you can use the following Tampermonkey script on Chrome, or something similar on other browsers. Be aware that there are no guarantees that it will work in the future
// ==UserScript==
// @name New Userscript
// @namespace http://tampermonkey.net/
// @version 0.1
// @description try to take over the world!
// @author You
// @match http://127.0.0.1:8080/*
// @grant GM_addStyle
// ==/UserScript==
(function() {
'use strict';
GM_addStyle("#content { width:1500px; }");
GM_addStyle("#content > div > div:nth-child(1) { width:70%; }");
GM_addStyle("#content > div > div:nth-child(2) { width:30%; }");
GM_addStyle("#folders .panel { width: 50%; float:left; margin-top: 0px; }");
})();