Customize Gnome terminal default size and position
From WickyWiki
Three different methods:
1. Start a terminal, go to Edit -> Profiles -> Default -> Edit and change "Use custom default terminal size"
2. Command-line <columns>x<lines>+<x position>+<y position>:
gnome-terminal --geometry 132x24+100+80
3. Settings file, modify ":co#132:it#8:li#24:\" (132 columns and 24 lines) in this file:
sudo gedit /usr/share/vte/termcap/xterm