In Ubuntu 8.04 also the same path:
/usr/share/vte/termcap/xterm
The default size is always 80 columns and 24 lines.
/usr/share/vte/termcap/xterm (part of the file is shown below)
You edit the default size by changing the line (displayed in bold below)
-----------
/usr/share/vte/termcap/xterm
-----------
# This is a cut-down version of the termcap file from my box with some entries
# removed (add them back in to override the terminal's behavior):
# kI (Insert, Delete is handled programmatically)
# kP/kN (Page Up, Page Down)
# ku/kd/kl/kr (Up, Down, Left, Right)
# k1/kd2/k3/k4/k5/k6/k7/k8/k9/k; (F1-F10)
# K1/K2/K3/K4/K5 (KP Up, Down, Left, Right, Begin)
xterm-xfree86|xterm-new|xterm terminal emulator (XFree86):\
:am:km:mi:ms:xn:\
:co#80:it#8:li#24:\ #change this line for your own default size
:AL=\E[%dL
C=\E[%dP
L=\E[%dM
O=\E[%dB:IC=\E[%d@:\
:LE=\E[%dD:\
:RI=\E[%dC:UP=\E[%dA:ae=^O:al=\E[L:as=^N:bl=^G:bt=\E[Z:\
:cd=\E[J:ce=\E[K:cl=\E[H\E[2J:cm=\E[%i%d;%dH:cr=^M:\
:cs=\E[%i%d;%dr:ct=\E[3g:dc=\E[P:dl=\E[M:do=^J:ec=\E[%dX:\
:ei=\E[4l:ho=\E[H:im=\E[4h:is=\E[!p\E[?3;4l\E[4l\E>:\
:kD=\177:\