you can achieve this with xrandr with the help of --fb --panning which you missed in your workout..
below are the working commands when I did it my system which are self explanatory..
my Original Screen Resolution is 1366x768 (eDP-1) and I tried to use 1000x768 leaving the blank space on Right
cvt 1000 766
xrandr --newmode BROKEN 62.00 1000 ...
The fbset program can apply a margin to any border. xrandr on the other hand only manages left and right borders simultaneously and/or top and bottom borders simultaneously for overscan / underscan.
You can read the man page on the internet:
set the length of one pixel (in picoseconds). Note that the frame ...