I understand. So there's a chance it simply works, and my problem may be the Thunderbolt conversion cable drama. Need to look more into that.

Regarding OSX Gatekeeper, that is easy to bypass. Simply right-click the installer and select Open from the menu. OSX probably assumes that you know what you're doing and offers an 'Open' option on the left hand side of the dialog. Select that and the thing installs. This so far worked for everything that Gatekeeper nagged about. Easy.

I used this way to install V5.6-beta2 and the installation went fine. Just not sure if it's worth anything. 😉

Best, Robert