[Ruatha]

Actually it shouldn't make any difference.
I belive everyone started with 2 billion people.
So if it got your atmosphere right (And if you've got 2 billion in pop you do) it shouldn't make any difference.
It's a medium sized ice instead of a medium sized gas, and they should both be able to support the same amount of people.

It can be a hassle to explain storywise though....