It would really depend per browser and user. Say for example you've optimized it for user A, who uses Chrome and has a very large screen real estate. Then user B comes along, who is using FireFox and has additional toolbars installed - this would decrease the height of the screen. Then user C doesn't like to browse with a maximized window, giving it an unusual width and height. And so on.
If you wish to guarantee that there's no cropping on either sides of the image, you'd have to use the "Normal" Display mode, and stretch it both vertically and horizontally. However, this would certainly make the models look alien - squished or stretched.