try this :

# bash

# 0x046018ae  0 xfce4-terminal.Xfce4-terminal  tosh Terminal - __ Rcran's private name here __

    wid=$( wmctrl -lx |awk '/rcran/ { print $1 }')

# man xdotool : 

    xdotool windowsize [options] [window] width height
    xdotool windowsize            $wid    600 400 

    xdotool windowmove [options] [window] x y
    xdotool windowmove           $wid     200 300  

    xdotool  windowsize $wid 600 400  windowmove $wid 200 300 


# rcran

    system( "wid=$( wmctrl -lx |awk '/rcran/ { print $1 }' ; xdotool windowsize $wid 600 400  windowmove $wid 200 300 " )