to change the default terminal window size you have to edit the file
gksudo gedit /usr/share/vte/termcap/xterm
and change the line (10) which reads something like
:co#132:it#8:li#26:\
where co#132 means 132 columns and li#26 means 26 lines .. dunno what the it#8 stands for .. it did not change anything altering it …