OEL Linux X11 resolution 1440X900

For a project I am running Oracle Enterprise Linux on my Macbook. The resolution of my MacBook Pro is 1440X900 so I also want this as the resolution of my Oracle Enterprise Linux installation within virtualbox. After installing the guest additions from virtualbox I had to addapt the content of the file /etc/X11/xorg.conf . There are a lot of guides online and hints online, some of them work some of them are not working. At least the below content was working for me an made Oracle enterprise Linux running with a 1440x900 resolution on my macbook pro.

# Xorg configuration created by system-config-display

Section "ServerLayout"
 Identifier     "single head configuration"
 Screen      0  "Screen0" 0 0
 InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "InputDevice"
 Identifier  "Keyboard0"
 Driver      "kbd"
 Option     "XkbModel" "pc105"
 Option     "XkbLayout" "us"
EndSection

Section "InputDevice"
 Identifier  "VBoxMouse"
 Driver      "vboxmouse"
 Option     "CorePointer"
EndSection

Section "Monitor"

### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
### Comment all HorizSync and VertSync values to use DDC:
 Identifier   "Monitor0"
 ModelName    "LCD Panel 1440x900"
### Comment all HorizSync and VertSync values to use DDC:
 HorizSync    31.5 - 56.0
 VertRefresh  56.0 - 65.0
       modeline  "800x600@56" 36.0 800 824 896 1024 600 601 603 625 +hsync +vsync
       modeline  "800x600@60" 40.0 800 840 968 1056 600 601 605 628 +hsync +vsync
       modeline  "1280x768@60" 80.14 1280 1344 1480 1680 768 769 772 795 -hsync +vsync
       modeline  "1280x720@60" 74.48 1280 1336 1472 1664 720 721 724 746 -hsync +vsync
       modeline  "1280x800@60" 83.46 1280 1344 1480 1680 800 801 804 828 -hsync +vsync
       modeline  "1440x900@60" 106.47 1440 1520 1672 1904 900 901 904 932 -hsync +vsync
 Gamma 1.0
EndSection

Section "Device"
 Identifier  "Videocard0"
 Driver      "vboxvideo"
EndSection

Section "Screen"
 Identifier "Screen0"
 Device     "Videocard0"
 Monitor    "Monitor0"
 DefaultDepth     24
 SubSection "Display"
  Depth     24
  Virtual 1440 900
  Modes  "1440x900@60" "1280x800@60" "1280x720@60" "1280x768@60" "800x600@60" "800x600@56"
 EndSubSection
EndSection