This is probably a long shot: is there any way to change the aspect ratio of the raytrace preview to match the renderer's?

Of course you can reshape the window itself, but the rendering canvas remains resolutely square. This isn't a problem if you're rendering square images, and with landscape / letterbox images it shows parts of the scene which won't be in the render. Distracting, but liveable-with. However if you're rendering portrait aspect images, the preview doesn't show the top and bottom of your production image, and that is irritating.

It would be nice if there was an INI file somewhere that one could edit, but if there is, I haven't found it. Like I said, it's a long shot, but I may as well ask!