add some more custom config and put every thing in comment in the custom.yaml template
/*
YUI 3.10.3 (build 2fb5187)
Copyright 2013 Yahoo! Inc. All rights reserved.
Licensed under the BSD License.
http://yuilibrary.com/license/
*/
YUI.add("uploader",function(e,t){var n=e.config.win;n&&n.File&&n.FormData&&n.XMLHttpRequest?e.Uploader=e.UploaderHTML5:e.SWFDetect.isFlashVersionAtLeast(10,0,45)?e.Uploader=e.UploaderFlash:(e.namespace("Uploader"),e.Uploader.TYPE="none")},"3.10.3",{requires:["uploader-html5","uploader-flash"]});