Key points
General information
<path-to-game>\Phant\DOSBOX\dosboxPHANT.conf
fullscreen=
false
windowresolution=
windowresolution=1280x960
output
output=opengl
<path-to-game>\Phant\DOSBOX\dosboxPHANT_single.conf
[cpu]
cycles=max
cycles=fixed 26800
~/.steam/steam/userdata/<user-id>/501990/