I really wanted to change the default terminal size on my Ubuntu machine and was really irritated by the fact that I couldn’t set the size I wanted even after customizing “Profiles”. A quick search on google helped me reach the link http://ubuntuforums.org/showthread.php?t=15471 which provided a decent solution towards the end of the thread there.
Quick Summary: Edit the file /usr/share/vte/termcap/xterm to modify the number of columns & rows there & restart all terminals. The relevant line in the file would look something like that shown below. To change the number of columns, change the co# number, in this case 80. To change the number of rows, change the li# number, in this case 24.