Make Sublime Text run in X11 without a window manager (kiosk mode)

I have a Chromebook Pixel that I'd like to use for development.  I'm interested in trying Sublime, but don't want to futz with a separate window manager.  Instead,  I'd like to have Sublime open in its own fullscreen X-window session. I can do everything else in ChromeOS.

I tried:

    exec subl

in ~/.xinitrc, which almost worked, except the window was the wrong size.  It looked like it was only taking up the first 640x480 of my display.  (Sorry I can't provide more accurate measurements.)

Is there a command line option to tell Sublime how big to draw itself?  I know this sounds like an obscure use case, but non of the Linux window managers look very good at high resolution, and the only thing I even need a separate Linux environment for is running Sublime.