I have found that most drivetrains have the drive wheels supported on both sides like the kitbot base. Some however have their drive wheels cantilevered on the outside of their base.
Here are 2 cantilevered bases. (very good robots)
http://www.chiefdelphi.com/media/photos/26944
http://www.chiefdelphi.com/media/photos/25814
Here are 2 non-cantillevered bases.
http://www.chiefdelphi.com/media/photos/28450
http://www.chiefdelphi.com/media/photos/27587
Which do you use? Why?
What are the advantages to each of them?