Because it has to fit in a 60" cylinder (as of right now, the metric number is different) we took the time to calculate out the total length of a robot + arm if it is 28" wide
We found that it could be 56.5" long. If your robot wasn't even an inch wide you would be able to be 60" long (essentially the diameter of the circle)
Equations here
http://en.wikipedia.org/wiki/Circular_segment
h(sub robot-width) is the width of your robot opposite the manipulator.
h(sub manipulator width) is the width of your manipulator (at its point furthest from the opposite side of the robot when it is parallel to the ground causes your manipulator to extend as far as possible (cos theta where theta = 0 in this case)