VNN_KCS, вон чего в мануале к FUSE написано. Только я ничего не понял из этого. К линуксу это что-ли?

DISPLAY SIZE

Some of Fuse's UIs allow resizing of the emulated Spectrum's display. For the window-based ones (GTK+ and Xlib), you can resize the window by, well, resizing it. :-) Exactly how this works depends on your window manager; you may have to make the window over twice the width and height of the original size before it actually scales up. Fuse attempts to keep the window `square', but with some window managers this can mean the window will never resize at all. If you experience this problem, the `--no-aspect-hint' option may help.

If you're using the SDL UI under X11, the window will automatically resize to be the correct size for the graphics filter selected.