Force 2560x1440 resolution on Dell 27" (U2711) LCD monitor

I have a Dell Latitude E6530 with VGA and HDMI output and the NVIDIA NVS 5200M graphics card. The VGA output can’t manage the full 2560x1440 resolution, and the HDMI output defaults to 1920x1080 due to an incorrect EDID reported by the U2711 monitor. Using various sources, including this post on Whirlpool, I managed to construct an xorg.conf that forces the full 2560x1440 resolution. If you use this on a desktop then you will probably have to change the ConnectedMonitor option, otherwise you’ll get a blank screen.

A cleaner fix would be to edit the EDID file to have the correct resolution (basically copying the Modeline information below) but I had no luck with Phoenix EDID Designer 1.3.

# /etc/X11/xorg.conf
# Make a backup of your original xorg.conf!

# File originally generated by nvidia Linux driver

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

Section "Files"
EndSection

Section "InputDevice"

    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"

    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"

    # Original values produced by nvidia:
    # HorizSync       28.0 - 33.0
    # VertRefresh     43.0 - 72.0

    # Tweaked values to get a 30Hz refresh rate to work:
    HorizSync       28.0 - 50.0
    VertRefresh     29.0 - 72.0
    Option          "DPMS"

    Option          "ModeDebug" "TRUE"
    Option          "UseEdid" "FALSE"
    Option          "ExactModeTimingsDVI"     "True"

    Modeline "2560x1440"  148.78 2560 2696 2968 3376 1440 1441 1444 1469 -hsync +vsync

    # How I calculated 148.78 for the 30Hz refresh rate:
    #
    # 30Hz rate:         ^^^^^^                ^^^^                ^^^^
    #                       c                     a                  b
    #
    # 30*(a/100)*(b/100)/100 = 148.78 = c

    Option "ModeValidation" "NoDFPNativeResolutionCheck"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    Option         "ConnectedMonitor" "DFP-3"
EndSection

Section "Screen"
    SubSection "Display"
        Depth 24
        Modes "2560x1440"
    EndSubSection
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
EndSection