X-Cart forums - Site speed and JS loading

So we've been having some serious problems with site speed in Google Analytics, and their top suggestions to fix this are to remove render blocking resources.

The majority if their suggested fixes involve jQueryUI calls, which appear in /skin/common_files/jquery_ui.tpl

Code:

{load_defer file="http://code.jquery.com/jquery-1.4.2.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.core.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.widget.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.position.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.mouse.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.button.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.dialog.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.resizable.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.draggable.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.tabs.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.datepicker.min.js" type="js"}

{load_defer file="lib/jqueryui/jquery.ui.effects.min.js" type="js"}

which itself is loaded in /skin/common_files/meta.tpl

Code:

{include file="jquery_ui.tpl"}

Along with other resources mentioned by Google

Code:

{load_defer file="js/ajax.js" type="js"}

{load_defer file="js/popup_open.js" type="js"}

{load_defer file="lib/jquery.blockUI.js" type="js"}

{load_defer file="lib/jquery.blockUI.defaults.js" type="js"}

I was under the impression that the whole load_defer thing was supposed to "fix" this, but apparently it doesn't. What do we need to do to prevent these items from slowing our site down without breaking something?