afaik, the window manager in maemo doesn't allow resizing or specification of window sizes. It can be done at compile time, but I don't know if the terminal source is available. if you use another window manager like kde or icewm then yes, you can certainly do what you are asking. Also, i'm sure you realize this, but the size in full screen is a higher resolution than what u desire anyway, but Im sure there must be a certain reason for this request.