OK,
go to the map, where the links are, edit scenario, save, and go to map
Press on the key board the Alt key and the comma key at the same time.
A screen should show up like this:
SINGLE PLAYER MULTIPLAYER
400x400
300x300
200x200
160x160
One should be slected. Click on whichever size you want, and press Escape (esc.). Your map size should change. I'll dl and rate the map ;)