I've never played this map, but I can assume it's rather annoying because of it's size. While the 250 territory objective would be a pretty big task in itself, it would seem to me at least, to make under dog victories impossible.
If you still have 100 territories left, I'd think you could still have a chance with some decent dice going your way, which does happen, and strategic moves. Then again I've never played the map, so what do I know. I'm sure an objective of some sort should be put into place here though.
When I posted the above, I was mainly talking about flat rate or no spoils. I completely forgot about escalating, which would give the under dog an even better chance at pulling out the win.