> Step 1:  M-x toggle-frame-maximized
 >
 > Step 2 [evaluate]:  (set-face-attribute 'default nil :font "-*-Courier-normal-normal-normal-*-18-*-*-*-m-0-iso10646-1")
 >
 > RESULT:  The frame substantially increases in size, going from maximized to extending well beyond the right edge of the screen.

That's bad.  Please try the attached patch (completely untested, might
crash your Emacs).

martin