Greater than 120x80 sizes?

[BlastHardcheese]

I imported my sweet map I made for Civ IV. It's pretty giant. Way larger than 120x80. However the game crashes when I try to play it unless I use the "scale map" option in worldbuilder to shrink it to 120x80. I love super giant maps and I tried changing the XML files to support x and y to 200. I even changed the Worlds.XML file to support 200x200 Huge maps but to no avail. I might not be using the modbuilder right but has anyone made a larger map than 120x80? And maybe give me some general instructions how to. I'm not sure if my computer cant handle it or the game cant work maps of that size.