If you have the ssl_xxx parameters set correctly in fop2.cfg, then IT WILL WORK. Perhaps you are editing the wrong fop2.cfg file as if you use Elastix and installed from RPM, then by default configuration files will be looked for on /etc/asterisk/fop2 instead of /usr/local/fop2. Another thing old FOP2 installs on elastix have is the configuration disableWebSocket in /var/www/html/fop2/js/presence.js set to true (it should be set to false).
Also be sure you use FOP 2.28 or higher...
To change the configuration location check the file /etc/sysconfig/fop2, if you see something like
OPTIONS="-d -c /etc/asterisk/fop2"
Then it indicates that you have configs on that directory, instead of /usr/local/fop2, so you should either modify the right config, or edit the OPTIONS line and leave it with "-d" so it will look for configs on /usr/local/fop2 directly (better this option if you upgrade FOP2 from the command line with wget).