@KNERD
I basically agree - OpenVPN can be setup in minutes - once you know what you are doing.
Actually the DO tutorial is outdated and doesn't work for the current CentOS 6.10 repos. Some file paths are different, easy-rsa needs to be installed separately and references easy-rsa 2.0, but yum install gives us 3.0. Most of the other google hits for "openvpn centos 6" had similar issues.
None of it is hard to overcome once you've done it a time or two, but could chase away a noob.
I haven't tested it yet, but the script @dicko linked looks pretty good. Unfortunately it doesn't do CentOS/SL 6. Still, it would be a great starting point if someone wanted to modify for IPBX usage. Some things should probably be changed if the purpose is only for remote phone access/management. I see no need for nat or enabling forwarding for such use.
I would run the script as
bash -x openvpn-install.sh
Override the whining about old OS's and see what stalls (likely unbound or somesuch)