Originally Posted by BashfulTux
Try in the device section for the primary display Option "UseDisplayDevice" "DFP" and for the secondary section Option "UseDisplayDevice" "CRT" and if you wanted to try the Xinerama use Option "DPI" "100x100" in the same sections for each device changing to the dpi you want set for each monitor.
Your solution worked perfectly! Thank you very much for your help!
Regarding Xinerama, I think it's not possible to have different dpi in each monitor, right?