Unfortunately, the game can only be run as fast as the slowest computer. I believe this is a result of its peer-to-peer nature.
An analogy would be 4 people meeting up to work on a project. If one person is slow, the rest must all wait, otherwise they'll get ahead of the fourth player. Since the 4th guy can't get any faster, he'll just get further and further behind. The only options are either to not include the fourth guy, or to meet up at a later time for him, delaying the rest of the group.
Now, server-client games basically mean you're either fast enough for the server, or you're getting like, a slideshow as everyone else zips by you, and your game is basically unplayable. This means the fourth guy simply can't play the game, which I'd argue is more unfair than having everyone else be a little slower.
