A person named Thomas O. in http://www.groupsrv.com/linux/post-755906.html answers this question with this:

“Resize the window to your liking and then right-click the titlebar and in the menu that comes up choose Advanced > Special Window Setting.”

“Go to the ‘Geometry’ pane and activate ‘Size’ and then pick ‘Apply Initially’ in the drop-down menu.”

As of this writing, I refuse to believe that this is only kind of place where this information is available.