When you doing the install and you reach to configuring the graphics settings in AVwizard, first you choose the connector and then the resolution, and then you change the User Interface (UI) to be used, the first is UI1 which is the lightest weight.
The file I mentioned is correct and located in /etc. If you compare the one on the core focusing on core only and media director only config, the one on core has autostart for core and MD configured to on, while the one on an MD has autostart for core off but MD on:
AutostartCore = 0
AutostartMedia = 1
I cannot verify if it works, have not tested it, simple used the UI1, which came in handy when my two MD's were in use by others, so I sat down by my core/hybrid and watch a pre-recorded episode of megastructures.
Also do not know if it will break anything, plan to try it out sometime.