How can I overclock my monitor to 80hz?

Still learning linux. Yes, my monitor supports 80hz, tested and confirmed on Windows.

So here's what I've tried to far.

1. cvt 1920 1080 80 + --newmode + --addmode in xrandr which resulted in

X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  18 (RRAddOutputMode)
  Serial number of failed request:  41
  Current serial number in output stream:  42

2. The good ol' EDID trick which doesn't work anymore. Results in a blank kernel cmd line. The moment I revert changes to /etc/X11/xorg.conf in root shell recovery mode everything boots normally.
3. Editing ViewPortIn in NVIDIA X Server Settings which results in my additions to it being deleted. I tried entering 1920x1080_80.00 and 1920x1080_80 which both get deleted before I can hit apply.

Any other ideas? Thanks.

xrandr outputs:

Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)
HDMI-0 disconnected (normal left inverted right x axis y axis)
DP-4 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 509mm x 286mm
   1920x1080     60.00*+
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1152x864      75.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   640x480       75.00    59.94  
DP-5 disconnected (normal left inverted right x axis y axis)

create modelines:

cvt 1920 1080 80

after use xrandr --newmode --addmode --outputmode