OK managed to figure this out ... sort of.
I am running a 710 RC1 32 bit core (DVD install) and I added the 64 bit MD above. As far as I know this should work but it doesn't seem to work for me.
Using the web admin I changed the MD to i386 and clicked rebuild image.
I now get the AV wizard and can configure the DVI output. I went through the media setup and everything seems fine but I am now getting a screen freeze after a minute of no activity. I have to reboot.
I can't add this as a working motherboard to the wiki as it still doesn't run that well. UI1 seems OK though.
To change from 64bit to 32bit you need to do the following;
Go to Web Admin -> Advanced -> Configuration -> Devices and select device template 28 "Generic PC as MD" and in the window that opens tick the "Allowed to Modify" tick box for the "#233 Model(string)" field. Then click "Save" at the bottom of the window.
Now go to Wizards -> Devices -> Media Directors and scroll to the MD you want to convert and edit the "Model" field to say "LMCE_MD_u0710_i386" and the "Architecture" field to say "i386" (**Omit the quotes when entering those strings into the fields**). Now click "Update" at the bottom of the page to save the changes. Then scroll back to the MD you want to convert and click the "Rebuid Image" button on the right hand side of the page next to the MD's entry.
Now wait... this can take a considerable amount of time and there is not much feedback that something is actually happening in the Web Admin page itself... after 10 mins or so a black window will appear and you will see some activity at last and then a small confirmation window will be displayed which you should confirm... and your done.
Its best to do this with the MD your converting powered off by the way... now boot the MD and it will startup and run the setup wizard etc.
Hope the above is helpful.
All the best