Yes, I looked into ~/.config/Terminal/terminalrc as per e.g. http://gnubyexample.blogspot.nl/2010...ize-fixed.html
fiddling with the MiscDefaultGeometry attribute may set the default
However, I want the screen location as it is at session save time
to be remembered. Fiddling with the geometry in .cache/sessions/xfce4-session-<host>:0 (outside of xfce) had an effect when restarting xfce. But only once: with the next logout/login the terminal is centered again.
From another, not updated yet Slackware box I know that the latter fiddling does not represent how things worked. In the .cache/sessions/xfwm4-xx...xx.state file there is a [GEOMETRY] attribute with values that may be the ones I am looking for. However fiddling there has no visual effects.
Maybe the screen location is saved but not picked up at restart ...