Set fullscreen resolution in advancedsettings.xls

Hi,

I currently have XBMC running in Linux Mint 15.

My screen resolution in Linux Mint is 1920X1080 and as such when I run XBMC in fullscreen
it runs at this same resolution. The problem is my PC cannot handle it running at that
resolution and takes ages to display and then I can not move around the menu's to
try and set the resolution to another lower one.

So could anyone tell me how and what code I need to use within an advancedsettings.xls
file so I can get XBMC to run in full screen at a lower resolution say: 1280x720

Also, if that resolution still does not work for me does could someone suggest
another lower resolution (as well as the relevant code to put into advancedsettings.xls)
that may work for me.


Thanks in advance