I don't remember if it also can make the full screen resolution to be larger, but ForeverZer0's Custom Resolution script works when making the windowed mode to be bigger.
Don't think he have posted it on this forum yet, if so, then I apologize for linking to another RPG Maker Forum =Phttp://forum.chaos-project.com/index.php/topic,7814.0.html
It was a while since I was into RPG Maker, but I still want to help with the things I can
Just test around with it. If it doesn't work the way you wanted, then maybe you can change it yourself to your liking.
Just remember that if the actual map is smaller than the resolution, it will cause some graphical glitches.