Also try to do anything you can in the room to increase your awareness of the room around the computer. Positioning the keyboard and mouse back farther from the screen (or moving the screen back farther from the keyboard), adding interestingly distracting posters to the wall behind the screen, increasing the room lighting behind the screen, etc., all of those things will help your brain realize that it's not actually inside that rendered world and not get the cue conflict problem.

And of course see if there's a way to tweak the config files to make the window even smaller.

I'm really interested in knowing how it goes.