You know...I don't know how much Sci-Fi you read, but are you familiar with Robert Silverberg's Majipoor? It's a gigantic world settled by humans....I think he got by the gravity thing by making the planet less dense: http://en.wikipedia.org/wiki/Majipoor_series

Just food for thought.

How about atmospheric density...if gravity acts more forcefully on the gasses (whatever their makeup) then they are under more pressure and will behave differently yes?

dlaporte