...and a margin width of 130 instead of the default 80 (because it's not 1983 anymore, you know.)
1280x800? I don't think that's a thing. Also a pixel width of 1280 could easily handle far more than a margin width of 80.
$ xrandr | head -n3Screen 0: minimum 8 x 8, current 1280 x 1520, maximum 32767 x 32767LVDS1 connected 1280x800+0+720 (normal left inverted right x axis y axis) 261mm x 163mm 1280x800 60.05*+
[…] (because it's not 1983 anymore, you know.)