Unless super London or Guangzhou get in the way, I think it's doable with size 17. It'll take some micromanaging and timing to get there but that's how it should be.
Quick question, shouldn't TortoiseSVN works fine with Windows 8?
Because it won't download files...
EDIT:
Command: Checkout from https://subversion.assembla.com/svn/Dawn_of_Civilization, revision HEAD, Fully recursive, Externals included
Error: Can't make directory 'C:\Program Files (x86)\Firaxis Games\Sid Meier's
Error: Civilization 4\Beyond the Sword\Mods\Dawn_of_Civilization': Access is denied.
Completed!:
I think I will remove embassies soon. The AI wastes too much time building them.