Can you limit the number of opponents in the retail game to a specific number?

[jimbob]

Neutrals are a wonderful gift, they make excellent slave labourers, and generally have a good homeworld. If you leave them long enough, they'll usually colonize the entire system, then you can go in and drop troops to take each planet over. This is followed by population movement to optimize the races on each planet by atmosphere type.

However I've never seen the computer successfully i) take over a planet or ii) move populations around to maximize "breath-ability". So the more neutrals, the bigger the advantage for the human...
... this is why my wife invariably napalms neutrals into the nether-world.