lol, L. Spiro, you know its possible
, but it would be a significant amount of work for L. Spiro to implement since it is specific to directx and opengl versions, not to mention it would compromise the program (graphic hooks are easily detected by modern anti-cheats). So, to incorporate this into the program is not very practicle, perhaps as a seperetly maintained module.
You are better off using an existing software package to handle this for you. See
http://www.gameoverlay.com/ , it will allow you to keep MHS full screen on desktop and in games.
Cheers